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1
Sternberg, Robert S. „Archaeomagnetism and magnetic anomalies in the American Southwest“. GEOPHYSICS 52, Nr. 3 (März 1987): 368–71. http://dx.doi.org/10.1190/1.1442311.
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Magnetic surveying is probably the most widely used geophysical technique at archaeological sites (Weymouth and Huggins, 1985). It is useful for locating features in which the magnetic susceptibility contrasts with the magnetic susceptibility of the surroundings because of induced and/or remanent magnetization. A contrast in magnetic induction can arise, for example, when the disturbed soil fill inside a formerly occupied room has a different magnetic susceptibility from the subsoil outside the room (Tite and Mullins, 1971). A contrast in magnetic remanence most commonly occurs when a baked clay artifact or feature such as a hearth has acquired a thermoremanent magnetization after being heated to several hundred degrees Celsius.
2
Noh, Kyubo, Ki Ha Lee, Seokmin Oh, Soon Jee Seol und Joongmoo Byun. „Numerical evaluation of active source magnetics as a method for imaging high-resolution near-surface magnetic heterogeneity“. GEOPHYSICS 82, Nr. 5 (01.09.2017): J27—J38. http://dx.doi.org/10.1190/geo2016-0435.1.
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We have evaluated a geophysical method that uses a low-frequency magnetic source to image subsurface magnetic heterogeneity. This active source approach can be used to image magnetic features at higher resolutions than the conventional passive geomagnetic method. Importantly, this frequency-domain active source approach is independent of the effects of remanent magnetization, which complicates the interpretation of geomagnetic data. We carried out forward modeling of frequency-domain electromagnetic (EM) data and we found that, at frequencies of a few hertz, the magnetostatic response due to the induced magnetization dominates the EM induction response. The result suggests that it is possible to make magnetic interpretation of low-frequency EM data without having to consider the conductivity structure and the corresponding EM induction effect. We compare the anomalous magnetic responses with magnetic noise components and find that the proposed active source magnetic (ASM) method has a depth of investigation of approximately 300 m. Free-space field and inductive noise are considered as the most important issues affecting the depth of investigation. We also determine the potential for linear interpretation of magnetic heterogeneity under 0.1 SI by showing that the low-frequency magnetic response can be approximated by a linear magnetic response. In our synthetic experiments, inversion of the ASM data shows a marked enhancement in resolution, with no effect of the remanent magnetization, in contrast to geomagnetic inversion. These results show that the ASM method is a useful geophysical tool, especially when high-resolution imaging of magnetic susceptibility is required or where strong remanent magnetization complicates the magnetic interpretation.
3
Abreu, H., J. R. Teodósio, J. Neto, M. Silva und C. S. Da Costa Viana. „The Influence of Molybdenum on the Texture and Magnetic Anisotropy of Fe–xMo–5Ni–0.05C Alloys“. Textures and Microstructures 31, Nr. 4 (01.01.1999): 231–38. http://dx.doi.org/10.1155/tsm.31.231.
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Diagrams of remanent induction, Br, versus saturation induction, Bs, for Fe–5Ni–xMo–0.05C alloys, where x is equal to 11%, 15% or 19%, were determined for samples 60%, 80%, 90% and 97% cold rolled and magnetically age-annealed at 610°C for 1h. The texture evolution in those alloys was analysed as a function of rolling reduction, by means of the orientation distribution function (ODF). The results show that a sharp {100} 〈110〉 texture component develops in the 11%-Mo alloy for rolling reductions in excess of 90%. This leads to the highest values of the remanent induction, Br, and of the Br/Bs ratio for this alloy as a result of 〈100〉 directions, the easy magnetization directions, lying at 45° to the rolling direction.
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FECHER, GERHARD H., DANIEL EBKE, SIHAM OUARDI, STEFANO AGRESTINI, CHANG-YANG KUO, NILS HOLLMANN, ZHIWEI HU et al. „STATE OFCoANDMnIN HALF-METALLIC FERROMAGNETCo2MnSiEXPLORED BY MAGNETIC CIRCULAR DICHROISM IN HARD X-RAY PHOTOELECTRON EMISSION AND SOFT X-RAY ABSORPTION SPECTROSCOPIES“. SPIN 04, Nr. 04 (Dezember 2014): 1440017. http://dx.doi.org/10.1142/s2010324714400177.
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The half-metallic Heusler compound Co2MnSi is a very attractive material for spintronic devices because it exhibits very high tunnelling magnetoresistance ratios. This work reports on a spectroscopic investigation of thin Co2MnSi films as they are used as electrodes in magnetic tunnel junctions. The investigated films exhibit a remanent in-plane magnetization with a magnetic moment of about 5 μBwhen saturated, as expected. The low coercive field of only 4 mT indicates soft magnetic behavior. Magnetic dichroism in emission and absorption was measured at the Co and Mn 2p core levels. The photoelectron spectra were excited by circularly polarized hard X-rays with an energy of 6 keV and taken from the remanently magnetized film. The soft X-ray absorption spectra were taken in an induction field of 4 T. Both methods yielded large dichroism effects. An analysis reveals the localized character of the electrons and magnetic moments attributed to the Mn atoms, whereas the electrons related to the Co atoms contribute an itinerant part to the total magnetic moment.
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Kruželák, Ján, Martina Matvejová, Rastislav Dosoudil und Ivan Hudec. „Barium and strontium ferrite-filled composites based on NBR and SBR“. Journal of Elastomers & Plastics 51, Nr. 5 (09.08.2018): 421–39. http://dx.doi.org/10.1177/0095244318792036.
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In the first part of the research, rubber magnetic composites were prepared by incorporation of strontium and barium ferrite in concentration scale ranging from 0 to 200 phr into rubber matrices based on acrylonitrile–butadiene rubber and styrene–butadiene rubber. The main objective was to investigate the influence of the type and content of magnetic filler on the cross-link density, physical–mechanical and magnetic characteristics of the prepared composites. In the second part of the study, the content of magnetic fillers was kept on constant level—200 phr and the main aim was to investigate the change in mutual combination of both fillers on the cross-linking and properties of the rubber magnets. The results revealed that both fillers show reinforcement effect in the rubber matrices. The higher tensile strength of composites was achieved by application of barium ferrite. Magnetic properties of composite materials were significantly influenced by magnetic characteristics of magnetic fillers. Higher remanent magnetic induction of barium ferrite was reflected in higher remanent magnetization of the equivalent composites. On the other hand, higher coercivity of strontium ferrite resulted in higher coercivity of strontium ferrite-filled composites.
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Huang, E.-Wen, Guo-Yu Hung, Soo Yeol Lee, Jayant Jain, Kuan-Pang Chang, Jing Jhe Chou, Wen-Chi Yang und Peter K. Liaw. „Mechanical and Magnetic Properties of the High-Entropy Alloys for Combinatorial Approaches“. Crystals 10, Nr. 3 (14.03.2020): 200. http://dx.doi.org/10.3390/cryst10030200.
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This review summarizes the state of high-entropy alloys and their combinatorial approaches, mainly considering their magnetic applications. Several earlier studies on high-entropy alloy properties, such as magnetic, wear, and corrosion behavior; different forms, such as thin films, nanowires, thermal spray coatings; specific treatments, such as plasma spraying and inclusion effects; and unique applications, such as welding, are summarized. High-entropy alloy systems that were reported for both their mechanical and magnetic properties are compared through the combination of their Young’s modulus, yield strength, remanent induction, and coercive force. Several potential applications requiring both mechanical and magnetic properties are reported.
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Dabas, Michel, und John R. Skinner. „Time‐domain magnetization of soils (VRM), experimental relationship to quadrature susceptibility“. GEOPHYSICS 58, Nr. 3 (März 1993): 326–33. http://dx.doi.org/10.1190/1.1443416.
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A comparison is made between measurements with a multichannel bipolar pulsed‐induction meter (PIM) and measurements made with a phase‐sensitive susceptibility bridge on more than 211 soil samples from a variety of archaeological sites in Europe. Eddy currents originating from the decay of viscous remanent magnetization (VRM) were measured with the PIM. The in‐phase and out‐of‐phase [Formula: see text] magnetic mass susceptibilies were measured with the susceptibility bridge. Viscous remanent magnetization was measured through eight time sampling intervals on the pulsed‐induction meter, and the linearity of VRM for selected samples was tested at various field strengths (200 to 2300 μT). It is believed that this extension of the reversible range indicates a high coercive strength of the magnetic grains in the soil samples involved. Whatever the origin of the soil sample, a constant decay of VRM with time was observed between 56 and 417 μs, after switching off the inducing field. This relation is shown to be a power law with exponent −1.4. This roughly agrees with a theoretical model that takes into account a finite‐energizing time of the transmitter pulse and single‐domain (SD) behavior of particles. Finally, a comparison is made between VRM and quadrature susceptibility [Formula: see text]. This comparison is in accordance with well dispersed single‐domain theory, and was found to be a linear relationship.
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Kruželák, Ján, Richard Sýkora, Rastislav Dosoudil und Ivan Hudec. „Rubber Composites Based on Polar Elastomers with Incorporated Modified and Unmodified Magnetic Filler“. Advances in Materials Science and Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/7242891.
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Rubber magnetic composites were prepared by incorporation of unmodified and surface modified strontium ferrite into rubber matrices based on NBR and NBR/PVC. Strontium ferrite was dosed to the rubber matrices in concentration scale ranging from 0 to 100 phr. The main goal was to investigate the influence of the type of ferrite on the curing process, physical-mechanical and magnetic properties of composites. The mutual interactions between the filler and rubber matrices were investigated by determination of cross-link density and SEM analysis. The incorporation of magnetic fillers leads to the increase of cross-link density and remanent magnetic induction of composites. Moreover, the improvement of physical-mechanical properties was achieved in dependence on the content of magnetic fillers. Surface modification of ferrite contributed to the enhancement of adhesion on the interphase filler-rubber. It can be stated that ferrite exhibits reinforcing effect in the composite materials and this reinforcing behavior was emphasized with the increase in polarity of the rubber matrix.
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Gao, Li, Qiu Hong Song und Jun Ting Yuan. „Effect of Continuous Annealing Parameters on the Microstructure and Magnetic Property of Cold Rolled Dual Phase Steel“. Advanced Materials Research 476-478 (Februar 2012): 241–47. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.241.
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The effect of continuous annealing parameters on the microstructure and magnetic property of cold rolled dual phase steel (DP steel) are investigated. Correlations of microstructure, magnetic properties and continuous annealing parameters are revealed. The mechanism of the magnetic property varying with continuous annealing process is also discussed. The results show that recrystallization is almost completed when heating to 740°C. For the DP steel soaked in the range of 770°C-830°C and quenched in different temperature, the TEM results indicate its microstructure mainly consists of the ferrite and martensite phase. The martensite volume fraction increases gradually with increasing the soaking and quenching temperature. It is found that magnetic properties of dual phase steel are very sensitive to continuous annealing process. With rising soaking and quenching temperature, the coercivity and hysteresis loss increase obviously, whereas the maximum permeability and the remanent induction tend to decrease.
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Thongsamrit, Wannisa, Thanida Charoensuk, Panissa Saetang, Pongsakorn Jantaratana, Chesta Ruttanapun und Chitnarong Sirisathitkul. „Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites“. Applied Sciences 11, Nr. 5 (26.02.2021): 2067. http://dx.doi.org/10.3390/app11052067.
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Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ–MnAl phase, as well as other phases. The nonmagnetic Al4C3 and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3–2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl–C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn3C phase, and magnetizations are likely increased by this phase.
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Kruželák, Ján, Andrea Kvasničáková, Rastislav Dosoudil und Ivan Hudec. „Magnetic composites based on NR and strontium ferrite“. Acta Chimica Slovaca 12, Nr. 1 (01.04.2019): 63–69. http://dx.doi.org/10.2478/acs-2019-0010.
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Abstract Two types of composites based on natural rubber (NR) and strontium ferrite were tested in this study. Composites of the first type were prepared by incorporation of strontium ferrite in the concentration range ranging from 0 to 100 phr (parts per hundred rubber) into pure NR based rubber matrix, while with those of the second type, strontium ferrite was dosed in the same concentration level into NR based rubber batch with constant amount of carbon black — 25 phr. For rubber matrices cross-linking, a standard sulfur based curing system was used. This work is focused on the effect of magnetic filler content on physico-mechanical, magnetic and thermo-physical properties of composite materials. Subsequently, the cross-link density and the structure of the formed sulfidic cross-links were examined. The results showed that the cross-link density of both types of composites increased with the increasing content of magnetic filler, while the structure of the sulfidic cross-links was almost not influenced by the amount of strontium ferrite. Tensile strength of rubber composites with pure rubber matrix was slightly improved by the incorporation of ferrite, while in case of composites based on a carbon black batch, the incorporation of magnetic filler resulted in the decrease of this characteristic. The presence of magnetic filler in both types of composites leads to a significant increase of the remanent magnetic induction.
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Billings, Stephen D., Leonard R. Pasion, Laurens Beran, Nicolas Lhomme, Lin-Ping Song, Douglas W. Oldenburg, Kevin Kingdon, David Sinex und Jon Jacobson. „Unexploded ordnance discrimination using magnetic and electromagnetic sensors: Case study from a former military site“. GEOPHYSICS 75, Nr. 3 (Mai 2010): B103—B114. http://dx.doi.org/10.1190/1.3377009.
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In a study at a military range with the objective to discriminate potentially hazardous [Formula: see text] mortars from nonhazardous shrapnel, range, and cultural debris, six different discrimination techniques were tested using data from an array of magnetometers, a time-domain electromagnetic induction (EMI) cart, an array of time-domain sensors, and a time-domain EMI cart with a wider measurement bandwidth. Discrimination was achieved using rule-based or statistical classification of feature vectors extracted from dipole or polarization tensor models fit to detected anomalies. For magnetics, the ranking by moment yielded better discrimination results than that of apparent remanence from relatively large remanent magnetizations of several of the seeded items. The magnetometer results produced very accurate depths and fewer failed fits attributable to noisy data or model insuffi-ciency. The EMI-based methods were more effective than the magnetometer for intrinsic discrimination ability. The higher signal-to-noise ratio, denser coverage, and more precise positioning of the EM-array data resulted in fewer false positives than the EMI cart. When depth constraints from the magnetometer data were used to constrain the EMI fits through cooperative inversion, discrimination performance improved considerably. The wide-band EMI sensor was deployed in a cued-interrogation mode over a subset of anomalies. This produced the highest-quality data because of collecting the densest data around each target and the additional late time-decay information available with the wide-band sensor. When the depth from the magnetometer was used as a constraint in the cooperative inversion process, all [Formula: see text] mortars were recovered before any false positives were encountered.
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Tanaka, Saburo, Takeyoshi Ohtani, Yosuke Uchida, Takumi Chigasaki und Yoshimi Hatsukade. „Metallic Contaminant Detection System Using Multi-Channel Superconducting Quantum Interference Device (SQUID)“. Solid State Phenomena 215 (April 2014): 465–69. http://dx.doi.org/10.4028/www.scientific.net/ssp.215.465.
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Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faradays law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID; as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system.
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Samardak, Alexey Y., Vladimir S. Pechnikov, Ekaterina V. Sukovatitsina, Alexander S. Samardak, Alexey V. Ognev, Liudmila A. Chebotkevich, Hadi Mahdizadeh, Alireza Akbari und Farzad Nasirpouri. „Temperature Dependence of Magnetic Saturation in Electrodeposited Nanocrystalline Nickel Films“. Solid State Phenomena 215 (April 2014): 292–97. http://dx.doi.org/10.4028/www.scientific.net/ssp.215.292.
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We report on experimental results of the temperature dependence of inductive (total) magnetic moment and remanent magnetic moment at saturation field for electrodeposited nanocrystalline Ni films with thicknesses ranging from 350 nm to 20 μm. We have found that the amplitude of roughness and crystallite size significantly affected the remanent saturation magnetic moment and coercivity.
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Wismogroho, Agus Sukarto, Wahyu Bambang Widayatno, Toto Sudiro und Didik Aryanto. „The Orientation Study of Ba-Sr Hexaferrite Particles by Parallel Magnetic Field Press“. Materials Science Forum 827 (August 2015): 223–28. http://dx.doi.org/10.4028/www.scientific.net/msf.827.223.
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It is well known that an orientation treatment on magnetic particles may increase magnetic flux density than that of those without treatment. In this work, the study on orientation of Barium Stronsium Hexaferrite (Ba-Sr Hexaferrite) particles using parallel system of magnetic field press was conducted to investigate the effect of powder orientation on its characteristic. Samples were compacted while the varied magnetic field induction were given, molded and then sintered at 1200°C for 1 hour. The measurement of magnetic properties showed that orientation process increased the value of magnetic remanence up to 173% (1264 Gauss). The magnetic field induction of 0.4 T was found to be the optimum value, where further increase of magnetic field did not give significant change. The crystal structure analysis showed the increase of peak of <001> plane which is correlated with the c-axis of Ba-Sr Hexaferrite crystal. In addition, the peak which is correlated with the opposite direction of c-axis disappeared, while the peaks between those directions decreased significantly. The micrograph of Ba-Sr Hexaferrite particles showed the alignment of c-axis parallel to the given magnetic field induction. These results showed the phenomenon of mechanical particle revolving and particle arrangement during the orientation process by which determined the obtained magnetic remanence.
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Radu, Florin, Vincent Leiner, Kurt Westerholt, Hartmut Zabel, Jeffery McCord, Alexei Vorobiev, Janos Major, David Jullien, Hubert Humblot und Francis Tasset. „Magnetic induction and domain walls in magnetic thin films at remanence“. Journal of Physics: Condensed Matter 17, Nr. 10 (26.02.2005): 1711–18. http://dx.doi.org/10.1088/0953-8984/17/10/025.
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Alwash, Nahedh H., Jafer Fahdel Odah und Ahmed Namah Mohamed. „"Effect of Substitution of Positive Ion (M+2) on the Physical Properties of M-Fe2O4 "“. Muthanna Journal of Pure Science 4, Nr. 1 (03.09.2017): 27–34. http://dx.doi.org/10.52113/2/04.01.2017/27-34.
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"Cobalt, Manganese and Magnesium ferrites powders have been synthesized using chemical mixing method. Calcination and sintering temperatures were 800oC respectively. The characteristics of spinal ferrite have been investigated by XRD technique while the magnetic characterization samples have been done using vibrating sample magnetometer (V.S.M). The magnetic properties such as initial magnetic permeability, quality factor, inductor factor and power loss density are studied under variation of frequency using L.C.R meter as well. Saturation magnetization, coercive field and remanent agnetization are determined from hysteresis loops for all prepared sample.
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Ktena, Aphrodite, und Evangelos Hristoforou. „Outlook of Preisach Modeling and Magnetic Non Destructive Testing“. Key Engineering Materials 543 (März 2013): 1–4. http://dx.doi.org/10.4028/www.scientific.net/kem.543.1.
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The Preisach formalism is used as a basis for a vector model of magnetic hysteresis in soft magnetic materials subject to tensile stress. The model uses as vector elementary hysteresis operator the Stoner-Wohlfarth mechanism of coherent rotation while the Preisach density is constructed as the weighed sum of probability density functions corresponding to the high and low induction regions. The model reproduces the basic phenomenology of stress-dependent hysteresis: the double peak in differential permeability modeled as the effect of internal demagnetizing fields emerging from residual stresses; the increase in coercivity due to increased pinning; the decrease in magnetic induction as the result of non-180o domain rotation. The role of the negative differential permeability near remanence and its derivative is discussed with respect to residual stresses and magnetic NDT.
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Nguyen, Thao A., Tadashi Yogi und Steven Lambert. „Microstructures and recording performances of longitudinal media using different atomic mass underlayer materials“. Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 758–59. http://dx.doi.org/10.1017/s0424820100088105.
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Magnetic and recording properties of Co-based longitudinal media are strongly influenced by the underlayer and sputtering conditions. We have investigated the relationship between magnetics, recording noise and microstructural characteristics of CoPtCr media on Mo and W underlayers over a sputtering pressure range 3-24 mtorr. complementing our earlier work of Cr underlayer.The media structure is C/CoPtCr/Mo or W, with thicknesses of 25/25/100 nm respectively. The film structure was sputter-deposited in a DC S-gun magnetron system. The remanence-thickness product, Mft, was kept in the range of 0.6-1.0 10-3 emu/cm2. The films were characterized by a vibrating sample magnetometer for their magnetic properties. Magnetic recording measurements were made with thin film inductive write heads with a track width of about 10 μm at a flying height of about 5 μm. The microstructures were studied using the IEOL JEM 4000 FX and AKASFII 002-B transmission electron microscopes.
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Yang, Yujie, und Xiansong Liu. „A study on the microstructural and magnetic properties of the Sr0.70-xBaxLa0.30Fe11.78Cu0.22O19 hexagonal ferrites“. International Journal of Modern Physics B 28, Nr. 21 (24.06.2014): 1450140. http://dx.doi.org/10.1142/s0217979214501409.
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Hexagonal ferrite Sr 0.70-x Ba x La 0.30 Fe 11.78 Cu 0.22 O 19 (0 ≤ x ≤0.7) magnetic powders and magnets were synthesized by the ceramic process. The phase compositions of the magnetic powders were investigated by X-ray diffraction. There is a single magnetoplumbite phase in the magnetic powders with barium content (x) from 0 to 0.70. The micrographs of the magnets were observed by a field emission scanning electron microscopy. All magnets have formed hexagonal structures and the particles are distributed evenly. Magnetic properties of the magnets were measured by a magnetic properties test instrument. The remanence, intrinsic coercivity, magnetic induction coercivity and maximum energy product of the magnets continuously decrease with the increase of barium content (x).
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Nguyen, Thao A., Tadashi Yogi und Steven E. Lambert. „The effect of sputtering pressure on microstructure and recording performance of high-density magnetic recording media“. Proceedings, annual meeting, Electron Microscopy Society of America 48, Nr. 4 (August 1990): 770–71. http://dx.doi.org/10.1017/s0424820100176988.
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Understanding the magnetic properties of thin films applicable to high density recording requires detailed knowledge of the microstructure and microchemistry of the film. Interactions such as exchange and magnetostatic as well as anisotropies have been shown theoretically to influence the magnetic properties and recording characteristics of the media. These magnetic interactions and anisotropies are very sensitive to microstructure. This study reports the efTcct of sputtering pressure on the microstructurc and magnetic properties of thin CoPtCr films. The relation between the microstructural features and the magnetic interactions will be discussed.The film structure, C/Co77Pt6Cr17/Cr, was sequentially sputtered onto Si and NiP/AlMg substrates precleaned by an rf plasma. The thicknesses were 25/25-60/100 nm respectively. Sputtering pressures ranging from 3 to 24 mtorr were investigated. The magnetic properties of the films (coercive field, Hc, coercive squareness, S*, remanent and saturation moments, Mrand Ms) were determined by vibrating sample magnetometry. The magnetic recording measurements were made with thin film inductive write heads and experimental shielded magnetoresistive read head with a track width of about 10μm. The head-media spacing was 5 μin. Noise voltages for transition densities up to 3000 fc/mm were determined in the usual fashion. The microstructures were studied using the JEOL JEM 2000 FX and 4000 EX transmission electron microscopes.
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Bai, Bo, Jun Zhou und Shengyun Wang. „Design of High-Performance Magnetorquer with Air Core for CubeSat“. Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, Nr. 1 (Februar 2018): 1–6. http://dx.doi.org/10.1051/jnwpu/20183610001.
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To solve the problem that how to design a big magnetic moment, small size, light weight, low power consumption magnetorquer with air core under the constraint of limited volume and power in CubSate, multiobjective optimization design method is used. Firstly, based on the structure of the square support with multiple layer of the enameled wire wrapped, the magnetic moment model, power consumption model and mass model are deduced from square support size, enameled wire diameter and turn number, respectively. Secondly, according to the model of magnetic moment and power consumption, the multi-objective optimization design of magnetorquer with genetic algorithm (GA) is used under the constraint of limited mass and volume. Thirdly, based on the relation between the magnetic moment and the magnetic induction intensity, the measurement method of the magnetic moment is designed. Finally, the designed parameter is implemented. The test result showed that the designed magnetorquer has the qualities of high linearity, low remanence, and it well met the requirements of CubeSat standard. The designed magnetorquer successfully applied in several CubeSats indicates the reliability of this design scheme.
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LIU, XIAOYA, LIANXI HU, YUPING LI und TAIQING DENG. „GRAIN TEXTURE, Nd CONTENT AND PROCESSING CONDITION EFFECTS ON MAGNETIC PROPERTIES OF NdFeB COMPOSITE MAGNETS“. Modern Physics Letters B 27, Nr. 19 (25.07.2013): 1341026. http://dx.doi.org/10.1142/s0217984913410261.
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The effects of grain texture, Nd content, processing conditions on magnetic properties and behavior of NdFeB nanocomposite magnet were investigated. The results demonstrate that mechanically activated disproportionation and desorption–recombination combined with plastic deformation process (M-HDDR & D) is an effective way to produce anisotropic NdFeB -type magnet. Magnetic anisotropy significantly enhances the magnetic properties of Nd 16 Fe 76 B 8 nanocomposite magnet, with the intrinsic coercivity (H ci ), magnetic induction (Br), and the energy product (BH) max achieving 0.88 T, 676.8 kA/m, and 135.2 kJ/m3, respectively. Decrease in Nd content improves the remanence but deteriorates the coercivity of NdFeB ternary composites. A low annealing temperature or short annealing time leads to an incomplete recombination, while a high temperature or long annealing time may result in grain overgrowth, and the optimum processing condition is found to be 780°C × 30 min. Pinning mechanism dominates in the magnetic hardening mechanism of Nd 16 Fe 76 B 8 composites prepared by both complete and incomplete recombination process, and particularly reversal nucleation process is also responsible for the latter case.
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Liu, Tong, Shicheng Zhang und Xingguo Li. „Synthesis and Characterization of Fe/Nd2O3 Core–Shell Nanoparticles by Hydrogen Plasma-Metal Reaction“. Journal of Nanoscience and Nanotechnology 6, Nr. 3 (01.03.2006): 743–47. http://dx.doi.org/10.1166/jnn.2006.17945.
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Fe/Nd2O3 core–shell nanoparticles (CSNs) with a mean diameter of 35 nm were produced successfully by using hydrogen plasma-metal reaction (HPMR) method. This core–shell structure was confirmed by high resolution transmission electron microscopy (HRTEM), energy dispersion X-ray spectroscopy (EDS), X-ray photoelectron spectral (XPS), and induction-coupled plasma (ICP) spectroscopy. The magnetic properties were measured by vibrating sample magnetometer (VSM). It was found that the mole ratio of Nd to Fe on the nanoparticle surface is 1.2:1, about 7 times of that of the whole nanoparticle. The saturation magnetization Ms and remanence Mr of Fe/Nd2O3 nanoparticles decrease prominently from Fe nanoparticles, whereas the coercivity HC drops only less than 5% of Fe nanoparticle. These CSNs have potential applications in magnetic and catalytic fields.
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Fourlaris, G., T. Gladman, M. Maylin, R. Lane und G. D. Papadimitriou. „TEM microscopical examination of the magnetic domain boundaries in a super Duplex austenitic-ferritic stainless steel“. Proceedings, annual meeting, Electron Microscopy Society of America 54 (11.08.1996): 1016–17. http://dx.doi.org/10.1017/s0424820100167548.
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It is well known that, due to the good corrosion resistance certain grades of stainless steels have significant applications in marine environments. For the development of certain large naval structures, in addition to the good corrosion resistance, other requirements are imposed such as high strength and toughness coupled with suitable magnetic characteristics.It has been demonstrated in an earlier publication that significant improvements in the coercivity, maximum induction and remanence values can be achieved, by using a 2205 type Duplex austenitic -ferritic stainless steel (DSS) instead of the low alloy medium carbon steels currently being used. These improvements are achieved in the as received 2205 material, and after small amounts of cold rolling have been applied, to increase the strength. In addition, the modification of the duplex austenitic-ferritic microstructure, via a heat treatment route, results in a finer austenite ‘island’ dispersion in a ferritic matrix and provides an attractive option for further modification of the magnetic characteristics of the material.
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Indrani, Decky Jusiana, Bambang Sunendar Purwasasmita, Wisnu Ari Adi und Jojor Simanjuntak. „Preparation and Characterization of Magnetic Carbonate Apatite/Chitosan/Alginate Composite Scaffold“. Materials Science Forum 827 (August 2015): 75–80. http://dx.doi.org/10.4028/www.scientific.net/msf.827.75.
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Treatment for bone cancer has begun to be experimented with ferrimagnetic for magnetic induction hyperthermia. On the other hand, composites of bioceramics and biopolymer have been studied for scaffold as these materials resemble the structure of bone. The current study investigated the magnetization of calcium aluminum ferrite magnetic (CaAl4Fe8O19) incorporated in carbonate apatite, alginate and chitosan, that serves as a scaffold. CaAl4Fe8O19 powder were synthesized using calcium nitrate, aluminium nitrate and ferrous chloride using the sol-gel method. Combining the carbonate apatite/chitosan/alginate compoiste and CaAl4Fe8O19using the freeze-dry method has produced carbonate apatite/alginate/chitosan/CaAl4Fe8O19 composite scaffolds. The CaAl4Fe8O19powder and the scaffolds were observed using SEM (scanning electrone microscope) and their magnetization were measured using VSM (vibrating sample magnetometer). It was shown that the scaffold is a composite structure of CaAl4Fe8O19 particles, having diameter ranging from 0.5 to 2 µm, embedded in the pore walls of the carbonate apatite/alginate/chitosan matrix. The saturation magnetization Ms and remanence magnetization Mr of the CaAl4Fe8O19particles were 20 and 2.0 emu/g, whereas, those of the magnetic scaffold were 4.3 and 2.0 emu/gr. The addition of the carbonate apatite/alginate/chitosan composite into CaAl4Fe8O19 decreased the fraction and/or magnetic of the CaAl4Fe8O19 particles.
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Fourlaris, G., T. Gladman und M. Maylin. „Microscopical Examination of a Super Austenitic Stainless Steel“. Microscopy and Microanalysis 3, S2 (August 1997): 687–88. http://dx.doi.org/10.1017/s1431927600010321.
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Stainless steels have significant applications due to their good corrosion resistance. However, for applications in a marine environment, i.e. for certain types of large naval structures, in addition to the good corrosion resistance, other requirements are imposed on the candidate material such as high strength and toughness coupled with suitable magnetic characteristics.It has been demonstrated in earlier publications that significant improvements in the coercivity, maximum induction and remanence values can be achieved, by using a 2205 type Duplex austenitic -ferritic stainless steel (DSS) instead of the low alloy medium carbon steels currently being used. These improvements are achieved in the as received 2205 material, and after small amounts of cold rolling have been applied, to increase the strength. However, the 2205 type DSS exhibits “ marginal” corrosion protection in a marine environment as well as exhibiting some measurable ferromagnetic response. Therefore, a study has been undertaken to examine the mechanical properties and microstructures obtained in a super austenitic stainless steel of the 254 SMO type.
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Narod, B. B. „The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors“. Geoscientific Instrumentation, Methods and Data Systems Discussions 4, Nr. 1 (19.06.2014): 319–52. http://dx.doi.org/10.5194/gid-4-319-2014.
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Abstract. 6-81.3 Mo permalloy, developed in the 1960s for use in high performance ring-core fluxgate sensors, remains the state-of-the-art for permalloy-cored fluxgate magnetometers. The magnetic properties of 6-81.3, namely magnetocrystalline and magnetoelastic anisotropies and saturation induction are all optimum in the Fe–Ni–Mo system. In such polycrystalline permalloy fluxgate sensors a single phenomenon may cause both fluxgate noise and magnetic hysteresis, explain Barkhausen jumps, remanence and coercivity, and avoid domain denucleation. The phenomenon, domain wall reconnection, is presented as part of a theoretical model. In the unmagnetized state a coarse-grain high-quality permalloy foil ideally forms stripe domains, which present at the free surface as parallel, uniformly spaced domain walls that cross the entire thickness of the foil. Leakage flux "in" and "out" of alternating domains is a requirement of the random orientation, grain-by-grain, of magnetic easy axes' angles with respect to the foil free surface. Its magnetostatic energy together with domain wall energy determines an energy budget to be minimized. Throughout the magnetization cycle the free surface domain pattern remains essentially unchanged, due to the magnetostatic energy cost such a change would elicit. Thus domain walls are "pinned" to free surfaces. Driven to saturation, domain walls first bulge then reconnect via Barkhausen jumps to form a new domain configuration this author has called "channel domains", that are attached to free surfaces. The approach to saturation now continues as reversible channel domain compression. Driving the permalloy deeper into saturation compresses the channel domains to arbitrarily small thickness, but will not cause them to denucleate. Returning from saturation the channel domain structure will survive through zero H, thus explaining remanence. The Barkhausen jumps being irreversible exothermic events are sources of fluxgate noise, powered by the energy available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which, are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B–H loop curvature (d2B/dH2). The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies fluxgate signal. B–H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire fluxgate signal with reduced noise.
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Humaidi, Syahrul, Ratna A. S, Tua Raja S, Seri Dermayu S und Perdamean S. „MAGNETIC PROPERTIES OF Cu2+ SUBSTITUTED BaFe12-xCuxO19 (x= 0.1,0.2,0.3,..., 4)“. INDONESIAN JOURNAL OF APPLIED PHYSICS 5, Nr. 01 (16.12.2015): 71. http://dx.doi.org/10.13057/ijap.v5i01.264.
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<p>Permanent magnet Barium M-Hexaferrite, BaFe<sub>12-x </sub>Cu<sub>x</sub> O<sub>19 </sub> was synthesized with a wide range of x (x = 0.1, 0.2, …, 3 and 4mole% respectively). The precursor was made by mixing BaCO<sub>3</sub> powder and Fe<sub>2</sub>O<sub>3</sub> powder, whereas CuO powder was used as additive. The powders were mixed together by wet milling in distilled water medium for 20 hours. The powders had been dried at a temperature of 100<sup>0</sup>C for 24 h before calcined at a temperature of 1100<sup>0</sup>C for 2 hours. The powders were then grained to prepare 400 mesh (38 µm) in diameter. The samples density was determined by using Archimedes method, magnetic properties by using permagraph, crystal structure by XRD-pattern and microwave absorbing properties using VNA. The hysteresis curve showed that the value of magnetic field ranging from 43.36 G to 100.42 G , remanence magnetic induction (Br) 20G-320G, coercivity (HcJ) 1.07 kOe to 9.22 kOe and energy production (BH) max from 0.05kGOe to 0.92 kGOe with a density from 3.82 g/cm<sup>3</sup> to 5.2 g/cm<sup>3</sup>. The effect of Cu doping tent to increase the value of density with an optimum magnetic properties at x=0.3%mole.</p>
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Narod, B. B. „The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors“. Geoscientific Instrumentation, Methods and Data Systems 3, Nr. 2 (29.09.2014): 201–10. http://dx.doi.org/10.5194/gi-3-201-2014.
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Abstract. Developed in the 1960s for use in high-performance ring-core fluxgate sensors, 6–81.3 Mo permalloy remains the state of the art for permalloy-cored fluxgate magnetometers. The magnetic properties of 6–81.3, namely magnetocrystalline and magnetoelastic anisotropies and saturation induction, are all optimum in the Fe–Ni–Mo system. In such polycrystalline permalloy fluxgate sensors, a single phenomenon may cause both fluxgate noise and magnetic hysteresis; explain Barkhausen jumps, remanence and coercivity; and avoid domain denucleation. This phenomenon, domain wall reconnection, is presented as part of a theoretical model. In the unmagnetized state a coarse-grain high-quality permalloy foil ideally forms stripe domains, which present at the free surface as parallel, uniformly spaced domain walls that cross the entire thickness of the foil. Leakage flux "in" and "out" of alternating domains is a requirement of the random orientation, grain by grain, of magnetic easy axes' angles with respect to the foil free surface. Its magnetostatic energy together with domain wall energy determines an energy budget to be minimized. Throughout the magnetization cycle the free-surface domain pattern remains essentially unchanged, due to the magnetostatic energy cost such a change would elicit. Thus domain walls are "pinned" to free surfaces. Driven to saturation, domain walls first bulge then reconnect via Barkhausen jumps to form a new domain configuration that I have called "channel domains", which are attached to free surfaces. The approach to saturation now continues as reversible channel domain compression. Driving the permalloy deeper into saturation compresses the channel domains to arbitrarily small thickness, but will not cause them to denucleate. Returning from saturation the channel domain structure will survive through zero H, thus explaining remanence. The Barkhausen jumps, being irreversible exothermic events, are sources of fluxgate noise powered by the energy available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring-core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B − H loop curvature [d2B/dH2]. The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies the fluxgate signal. B − H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire the fluxgate signal with reduced noise.
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Nasruddin, M. N., Tulus Ikhsan Nasution, M. S. Achmad, K. Candra, F. N. Lukman, P. Sebayang und Irwana Nainggolan. „The Influence of Sintering Temperature and Mn-Ti Doped BaFe12O19 on the Microwave Absorbing Properties“. Applied Mechanics and Materials 754-755 (April 2015): 733–37. http://dx.doi.org/10.4028/www.scientific.net/amm.754-755.733.
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The effect of sintering temperature and Mn-Ti (x = 0.1 and 0.5 % mol) doped in Barium hexaferrite (BaFe12O19) on the microwave absorption properties have been investigated. The BaFe(12-2x)MnxTixO19samples were prepared by using a solid state reaction method from technical grade materials of BaCO3, Fe2O3, MnO2, and TiO2. The permagraph and vector network analyzer (VNA) measurement with frequency of 4 – 10 GHz were used to determine the magnetic properties and microwave absorbing properties, respectively. The magnetic induction and magnetizing force (B-H) curve analysis of BaFe(12-2x)MnxTixO19revealed that by increasing the Mn-Ti dopant concentrations, the remanence (Br) and BH(max) increases, meanwhile, the HCBvalue decreases for both 1100 and 1150oC. The frequency dependence of reflection loss (RL) measurement given anoptimum value of-26.15 dB at frequency of 9.18 GHz which obtained by x = 0.1% mol Mn-Ti (1100oC). The maximum absorption peak was achieved for 0.5 % mol Mn-Ti sample with ~98.3 % at 9.18 GHz. By controlling the sintering temperature and Mn-Ti dopant concentration, the RL and absorption behavior can be modified to desirable values and also indicates that higher Mn-Ti dopant concentration (0.5% mol) possess better absorbing characteristics. Furthermore, it was found that complex permitivitty and permeability values of BaFe12O19can be modified by controlling the Mn-Ti dopant concentration.
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Mani, Mahesh Kumar, Giuseppe Viola, Mike J. Reece, Jeremy P. Hall und Sam L. Evans. „Structural and magnetic characterization of spark plasma sintered Fe-50Co alloys“. MRS Proceedings 1516 (2012): 201–7. http://dx.doi.org/10.1557/opl.2012.1669.
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ABSTRACTFe-50 wt% Co alloy powders with average particle size of 10 μm were compacted by spark plasma sintering (SPS) at 700, 800, 900 and 950oC by applying 40, 80, 100 MPa uniaxial pressures for 2, 5, 10 minutes. The densities of the samples were found to increase with temperature from 700 to 900oC for constant sintering pressure and time and to decrease for the material sintered at 950oC. The effects of sintering time on density were more significant in samples sintered at 700oC and 800oC than those densified at 900oC. The consequences of small increases in mechanical pressure during sintering on density values were significant for samples sintered at 700oC. The coercivity (Hc) of the compacts decreased significantly with increasing sintering temperature, and with increasing dwell time at sintering temperatures lower than 700oC. The sample sintered at 950oC, which contains the largest grains among the prepared samples and porous microstructure, exhibited the minimum coercivity. Unlike Hc, the remanence (Br) and saturation induction (Bsat) values were more strongly affected by the specimen density than by grain size. Br and Bsat values were found to vary linearly with sintering temperature and pressure owing to increasing density. An increase in soaking time at 800 and 900 oC, although enabling higher density, exhibited contradicting effects on Bsat values. The SPS parameters to obtain maximum density and optimum magnetic properties for Fe-50% Co alloy were found to be 900oC, 80 MPa and 2-5 minutes.
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Raghasudha, M., D. Ravinder und P. Veerasomaiah. „Electrical and Magnetic Properties of Mg-Cr and Co-Cr Nano Ferrites Synthesized by Citrate-Gel Method“. Solid State Phenomena 241 (Oktober 2015): 69–92. http://dx.doi.org/10.4028/www.scientific.net/ssp.241.69.
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The work deals with the study of electrical and magnetic properties of Magnesium-Chromium and Cobalt-Chromium nanoFerrites for their potential applications synthesized by Citrate-Gel auto-combustion method. Structural Characterization of prepared nanoferrites was performed using XRD, SEM, EDS and TEM. XRD patterns confirmed the formation of homogeneous single phased cubic spinel belonging to the space group Fd3m (in agreement with ICSD Ref. data). It is found that crystallite size of Mg-Cr ferrites was in the range of 7-23nm and that of Co-Cr nanoferrites in the range of 6-12 nm. Structural morphology of both the ferrites was studied by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy). Elemental compositional analysis was carried out by EDS.Electrical properties such as D.C. resistivity of prepared Mg-Cr and Co-Cr nanoferrites were studied by two probe method. The dielectric measurements as a function of frequency at room temperature were performed in the frequency range of 20Hz to 2MHz using LCR meter. Various dielectric parameters like dielectric constant (ε′), dielectric loss (ε′′) and dielectric loss tangent (tan δ) were measured as a function of frequency. The magnetization measurements of the prepared nanoferrite samples were carried out at room temperature in the applied field of ±15KOe using Vibrating Sample Magnetometer (VSM). From the obtained M-H loops, various magnetic parameters such as Saturation Magnetization (Ms), Coercivity (Hc) and Remanence Magnetization (Mr) were measured. Magnetization as a function of field (±10T) at 5K, 25K, 300K temperatures was measured using VSM. Super-paramagnetic nature of some specified samples in Mg-Cr nanoferrites system was investigated from the temperature dependence of both the field cooled (FC) and the zero-field cooled (ZFC) magnetization measurements under a field of 100 Oe in the temperature range 5K to 350K.From the results of D.C. resistivity measurements it is observed that the resistivity decreases with increase in temperature for both Mg-Cr and Co-Cr nanoferrites suggesting the semiconducting behavior of the samples. Dielectric measurements suggest that the conduction in the ferrite systems may be due to the polaron hopping mechanism. The low loss tangent values at high frequency show the potential applications of these materials in high frequency microwave devices. Mg-Cr nanoferrites were synthesized yielding narrow hysteresis loops which are the characteristic of very soft magnetic materials that are desirable for their utility in Transformers, Inductor cores, Microwave devices and Magnetic shielding. Hysteresis loops of Co-Cr nanoferrites show the medium hard magnetic behavior of the materials. MgFe2O4 shows superparamagnetic behavior above room temperature and MgCr0.9Fe1.1O4 shows superparamagnetic behavior with the blocking temperature 94.5K. Hence these nanoferrites find applications in targeted drug delivery and in Magnetic Resonance Imaging (MRI) in biomedical field. The observed results can be explained in detail on the basis of composition and crystallite size.Contents of Paper
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Borodko, Y. G., Bokhimi, D. Acosta, L. M. Ioffe, T. Viveros, P. Bosch und N. Nava. „Structural and Magnetic Properties of γ-Fe2O3 Particles Coated with TiO2“. MRS Proceedings 403 (1995). http://dx.doi.org/10.1557/proc-403-725.
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Kadin, A. M., R. W. McCallum, G. B. Clemente und J. E. Keem. „Melt-Spun Permanent Magnet Alloy with Enhanced Isotropic Remanence“. MRS Proceedings 80 (1986). http://dx.doi.org/10.1557/proc-80-385.
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AbstractRapid solidification onto a copper quench surface (melt-spinning) has been used to fabricate a high-performance permanent magnet alloy (Ovonic Hi-Rem™) based on the Nd-Fe-B class of materials. Crucial idditions of alloying elements are combined with careful control over quench parameters to yield a random assembly of microcrystallites, with macrosconically isotropic magnetic properties including values of remanent induction that can exceed 10 kG and maximum energy products greater than 20 MGOe. These values exceed those expected from conventional randomly oriented magnets. The enhanced magnetic performance is related to results of x-ray diffraction and electron microscopy.
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Kasama, Takeshi, Rafal E. Dunin-Borkowski, Michael R. Scheinfein, Steven L. Tripp, Jie Liu und Alexander Wei. „Off-Axis Electron Holography of Self-Assembled Co Nanoparticle Rings“. MRS Proceedings 1026 (2007). http://dx.doi.org/10.1557/proc-1026-c18-03.
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AbstractWe use off-axis electron holography in the transmission electron microscope (TEM) to study magnetic flux closure (FC) states in self-assembled nanoparticle rings that each contain between five and eleven 25-nm-diameter Co crystals. Electron holograms are acquired at room temperature in zero-field conditions after applying chosen magnetic fields to the samples in situ in the TEM by partially exciting the conventional microscope objective lens. Mean inner potential contributions to the phase shift are determined by turning the samples over, and subsequently subtracted from each recorded phase image to obtain magnetic induction maps. Our results show that most nanoparticle rings form FC remanent magnetic states, and occasionally onion-like states. Although the chiralities (the directions of magnetization) of the FC states are determined by the shapes, sizes and positions of the constituent nanoparticles, reproducible magnetization reversal of each ring can be achieved by using an out-of-plane magnetic field of between 1600 and 2500 Oe.
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„Optimization of methods of nondestructive inspection of the quality of components on the basis of remanent magnetic induction“. NDT International 22, Nr. 1 (Februar 1989): 55. http://dx.doi.org/10.1016/0308-9126(89)91314-x.
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He, Cunfu, Wenqiao Dou, Xiucheng Liu, Meng Yang und Ruifang Zhang. „A Sensitivity Mapping Technique for Tensile Force and Case Depth Characterization Based on Magnetic Minor Hysteresis Loops“. Chinese Journal of Mechanical Engineering 33, Nr. 1 (25.11.2020). http://dx.doi.org/10.1186/s10033-020-00508-5.
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AbstractIn the nondestructive testing and evaluation area, magnetic major hysteresis loop measurement technology are widely applied for ferromagnetic material evaluation. However the characterization ability of major hysteresis loop measurement technology greatly varies as the evaluated target properties. To solve this limitation, magnetic minor hysteresis loops, which reflect the responses of ferromagnetic material magnetization in a systematic way, is recommend. Inspired by plenty of information carried by the minor loops, the sensitivity mapping technique was developed to achieve the highest sensitivity of minor-loop parameters to the nondestructively evaluated targets. In this study, for the first time, the sensitivity mapping technique is used to measure the tensile force in a steel strand and evaluate the effective case depth in induction-hardened steel rods. The method and procedures for the sensitivity mapping technique are given before experimental detection. The obtained experimental results indicate that the linear correlation between the induced voltage (or the magnetic induction intensity) and the tensile force (or effective case depth) exists at most of the locations in the cluster of minor loops. The obtained sensitivity maps can be used to optimize the applied magnetic field (or excitation current) and the analyzed locations at the minor loops for achieving the highest sensitivity. For the purpose of tensile force measurement, it is suggested that the strand should be firstly magnetized to the near-saturation state and then restored to the remanent state. In this way, the highest sensitivity is obtained as about 15.26 mV/kN. As for the induction-hardened steel rods, the highest sensitivity of magnetic induction intensity to the effective case depth occurs under low magnetic field conditions and the absolute value of the highest sensitivity is about 0.1110 T/mm. This indicates that if the highest sensitivity is required in the case depth evaluation, the induction-hardened steel rods are only required to be weakly magnetized. The proposed sensitivity mapping technique shows the good performance in the high-sensitivity evaluation of tensile force and case depth in ferromagnetic materials and its application scope can be extended to other nondestructive detection fields.
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Ferreira, Francisco José Fonseca, Raimundo Almeida Filho und Francisco Valdyr Da Silva. „MODELAGEM DE DADOS AEROMAGNÉTICOS PARA ESTIMAR LARGURA E ESPESSURA DO COMPLEXO MÁFICO/ULTRAMÁFICO DE CAMPO FORMOSO-BA“. Boletim Paranaense de Geociências 52 (30.06.2003). http://dx.doi.org/10.5380/geo.v52i0.4199.
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O complexo máfico/ultramáfico Campo Formoso, no estado da Bahia, é constituído por rochas metamórficas de alto grau, derivadas de peridotitos e piroxenitos do Proterozóico Inferior. Em superfície, ele estende-se por cerca de 40 km, com larguras variando entre 100 e 1.100 metros. A despeito de encerrar as mais importantes mineralizações de cromo conhecidas no Brasil, os conhecimentos geológicos sobre o complexo ainda são bastante limitados. O profundo intemperismo e a presença de coberturas aluviais e coluviais dificultam o mapeamento geológico dessas rochas. Estimativas sobre largura e espessura do complexo em subsuperfície são importantes, visto que, por tratar-se de um corpo estratiforme, níveis mineralizados em superfície podem prolongar-se até grandes profundidades. Neste estudo, dados aeromagnéticos são analisados visando a obter informações sobre a extensão do complexo em subsuperfície. Para isso, um método interativo de modelagem de corpos magnéticos tabulares por processo de inversão foi empregado em uma área selecionada, onde ocorrem alguns dos mais importantes depósitos de cromo conhecidos no complexo. A técnica de modelagem empregada permite o cálculo de parâmetros tais como mergulho, largura e espessura de corpos de geometria simples, magnetizados por indução, remanência, ou ambos. O algoritmo empregado usa valores iniciais para cada parâmetro do corpo a ser modelado, os quais podem ser modificados pelo analista, de modo a incorporar dados reais. Esses dados são manipulados interativamente na busca de um "melhor ajuste", de modo que os parâmetros ajustados caiam dentro de limites de tolerância especificados pelo usuário. A qualidade do ajuste é medida pela relação da soma ponderada dos desvios quadráticos entre valores observados e calculados. Tomando-se como base a geologia da área de estudo, selecionou-se o modelo de dique espesso finito tabular 2 (2¾-D) como o mais apropriado para representar o complexo. Os resultados de modelagens em três perfis indicaram corpos magnéticos com larguras variando entre 264 e 374 metros, espessuras entre 432 e 470 metros e mergulhos entre 52o e 68o para SE. MODELING AIRBORNE MAGNETIC DATA TO ESTIMATE WIDTH AND THICKNESS OF THE MAFIC/ULTRAMAFIC COMPLEX OF CAMPO FORMOSO, BAHIA STATE, BRAZIL Abstract The Campo Formoso complex is located in the Bahia State, in the northeastern part of Brazil. The complex comprises high-grade metamorphic rocks derived from peridotite and pyroxenite of Early Proterozoic age. Mafic/ultramafic rocks cover an area approximately 40 km long and 100 to 1100 m wide, with a general NE-SW direction, dipping to the southeast. This complex hosts the most important chromium deposit of Brazil. This deposit occurs in the southern portion of the complex which makes up a lower structural block, better preserved by the erosion than the northern portion. In spite of its economic importance, geological knowledge of the complex is still very limited. The deep weathering of the mafic/ultramafic rocks and the presence of alluvial and colluvial deposits difficult geological mapping. It is a stratiform complex and the mineralized layers may extend down to great depths. Therefore it is important do know the width and thickness of its rocks in subsurface. In this study airborne magnetic data were analyzed to obtain information of the subsurface extent of the Campo Formoso complex. In order to do that an interactive modeling method of tabular magnetic bodies with inversion process was applied in a selected area of the southern portion of the complex. The used model calculates depth, thickness, and dip of a simple geometry body, magnetized by induction, remanence, or both. This procedure helps to find the best possible match between a theoretical anomaly and a given set of magnetic data. The best fit is found when the adjusted parameters fall within a user-specified tolerance of values which minimize the weighted sum of squared deviations between the observed and the theoretical magnetic anomaly. When a set of parameters satisfies the best-fit criterion, confidence ranges are calculated for all parameters. According to geological data, the best model assumed for the ore body was a thick, flat-topped dyke of finite strike length 2 (2¾-D) and a finite variable depth extent. The modeling results of three profiles of the study area indicate magnetized bodies varying width from 264 to 374 m, thickness from 432 to 473m, and dipping from 52o to 68o SE.