Статті в журналах: "Magnetic Anisotrophy Enhancement"

1

Yuan, Xiao, P. S. Riseborough, Eleonir Calegari, and Sergio Magalhaes. "Enhanced Spin Orbit Interaction in Actinides." Journal of Physics: Conference Series 2164, no. 1 (March 1, 2022): 012059. http://dx.doi.org/10.1088/1742-6596/2164/1/012059.

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Abstract We investigate the effect of many-body interactions on the spin-orbit coupling of anisotropic metals. We use the Underscreened Anderson Lattice Model that was proposed to describe actinide compounds. The Coulomb interactions induce off-diagonal correlations that enhance the components of the spin-orbit coupling. Modest values of the Coulomb interaction U can significantly enhance the spin-orbit coupling and effect the electronic spectrum. The enhancements are most pronounced for systems that are on the verge of magnetic instabilities. The enhancement is anisotropic in crystals with non-cubic symmetries and can lead to giant magnetic anisotropies in paramagnetic states.

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2

Wu, J. X., X. T. Zhao, W. Liu, Y. Li, J. Ma, Y. H. Song, L. Liu, H. Z. Ju, and Z. D. Zhang. "Magnetic properties and coercivity mechanism of high Ce-content CeNdFeB film with Tb diffusion." Journal of Applied Physics 131, no. 16 (April 28, 2022): 163901. http://dx.doi.org/10.1063/5.0088463.

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Magnetic properties and coercivity mechanism of an anisotropic Ce–Nd–Fe–B film with a high Ce content (70 at. % Nd is replaced by Ce) have been investigated. After grain boundary diffusion with Tb layers, an enhancement of coercivity from 4150 to 9250 Oe is observed. Combining the initial magnetization curves, micromagnetic theory, and in-siut observation of magnetic domains in the demagnetization process, it is confirmed that the coercivity mechanism for the high-Ce-content magnets is the mixed type dominated by the pinning mechanism. Moreover, as the thickness of the Tb diffusion layer increases, the pinning center of domain walls changes from narrow planar inhomogeneities to wide planar inhomogeneities. A growing role of pinning plays in determining the coercivity of samples with increasing the thickness of Tb layer due to the increase in magnetocrystalline anisotropy after Tb substitution in the RE2Fe14B phase. In addition, the CeFe2 intergranular phase leads to the enhancement of coercivity due to decoupling the hard magnetic phase grains. Our results provide an insight into the coercivity mechanism of high-Ce-concentration Ce–Nd–Fe–B magnetic materials and promote the comprehension of the effect of Tb diffusion in the magnetization reversal process.

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3

Bartolomé, Juan, F. Luis, L. M. García, F. Bartolomé, F. Petroff, C. Deranlot, F. Wilhelm, A. Rogalev, P. Bencok, and N. B. Brookes. "Anisotropy Enhancement in Co Granular Multilayers by Capping." Materials Science Forum 570 (February 2008): 1–9. http://dx.doi.org/10.4028/www.scientific.net/msf.570.1.

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The effect of capping with Cu, Au and Pt of an array of Co nanoparticles is revised. The magnetic surface anisotropy KS was found to be the dominant contribution to the effective anisotropy Keff of the particles. Recent X-ray Magnetic Circular Dichroism (XMCD) measurements show that there is hybridization between the 3d Co electrons and the d and 4p electrons of the capping metal. By comparison to the mechanisms which give rise to the surface anisotropy in thin films, it is argued that this hybridization governs the modification of KS, and hence, of Keff.

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4

BARONIA, A., and M. S. TIWARI. "Kinetic Alfvén waves in an inhomogeneous anisotropic magnetoplasma in the presence of an inhomogeneous electric field: particle aspect analysis." Journal of Plasma Physics 63, no. 4 (May 2000): 311–28. http://dx.doi.org/10.1017/s0022377899008272.

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Kinetic Alfvén waves in the presence of an inhomogeneous electric field applied perpendicular to the ambient magnetic field in an anisotropic, inhomogeneous magnetoplasma are investigated. The particle aspect approach is adopted to investigate the trajectories of charged particles in the electromagnetic field of a kinetic Alfvén wave. Expressions are found for the field-aligned current, the perpendicular current, the dispersion relation and the particle energies. The growth rate of the wave is obtained by an energy- conservation method. It is predicted that plasma density inhomogeneity is the main source of instability, and an enhancement of the growth rate by electric field inhomogeneity and temperature anisotropy is found. The dispersion relation and growth rate involve the finite-Larmor-radius effect, electron inertia and the temperature anisotropy of the magnetoplasma. The applicability of the investigation to the auroral acceleration region is discussed.

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5

Anyfantis, Dimitrios I., Camillo Ballani, Nikos Kanistras, Alexandros Barnasas, Vassilios Kapaklis, Georg Schmidt, Evangelos Th Papaioannou, and Panagiotis Poulopoulos. "Growth, Magnetic Anisotropies and Exchange Bias of Thin Ni0.95Fe0.05/NiFeO Multilayers." Coatings 12, no. 5 (May 4, 2022): 627. http://dx.doi.org/10.3390/coatings12050627.

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Ni0.95Fe0.05/NiFeO multilayers were fabricated by radio frequency magnetron sputtering and natural oxidation. Doping of Ni by only 5 at. % Fe results in enhanced layering quality as X-ray reflectivity reveals. Due to magnetostatic anisotropy, the multilayers were found to be in-plane magnetized. The influence of mild thermal annealing (T = 525 K) on the magnetic properties of NiFe/NiFeO multilayers is also investigated. Annealing results in the enhancement of perpendicular magnetic anisotropy, mainly due to an increase in the uniaxial volume anisotropy term. Temperature-dependent hysteresis measurements between 4–400 K revealed considerable enhancement of coercivity and appearance of exchange bias effect.

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6

Komogortsev, S. V., N. A. Chizhik, E. Y. Filatov, S. V. Korenev, Y. V. Shubin, D. A. Velikanov, Rauf S. Iskhakov, and G. Y. Yurkin. "Magnetic Properties and L1₀ Phase Formation in CoPt Nanoparticles." Solid State Phenomena 190 (June 2012): 159–62. http://dx.doi.org/10.4028/www.scientific.net/ssp.190.159.

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The effect of the atomic disorderorder transformation on remanence, coercivity and magnetic anisotropy energy in CoPt nanoparticles prepared by thermal decomposition and annealed at 400°C for 4 and 16 hours has been studied. The observed remanence and magnetic anisotropy energy enhancement versus annealing time are discussed in the terms of ordering domain formation inside nanoparticles.

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7

Wang, Xujie, Zhenlong Dou, Chi Zhang, FangFang Deng, XiaoLin Lu, ShuangShuang Wang, Li Zhou, and Tao Ding. "Polarization-controlled anisotropy in hybrid plasmonic nanoparticles." Nanophotonics 11, no. 5 (January 27, 2022): 1003–9. http://dx.doi.org/10.1515/nanoph-2021-0691.

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Abstract Anisotropy has played a critical role in many material systems, but its controllable creation and modulation have been a long-lasting challenge for the scientific communities. Polarization-addressed anisotropy appears more attractive among all approaches due to its excellent controllability, simplicity, and accuracy, but only a limited number of material systems are applicable for such a concept, which are largely focused on oriented growth. Here, we establish a polarization-dependent anisotropic etching system made of Au@oligomer core–shell nanoparticles (NPs). As the oligomer coatings can be photochemically degraded via two-photon photolithography, the plasmonic near-field enhancement supported by the Au NP cores renders much faster degradation of the oligomer shells along the polarization, resulting in anisotropic Au@oligomer hybrid NPs. Such shape anisotropy leads to polarization-dependent photoluminescence with embedded dyes of methylene blue, which can be used as single-particle-based polarization detector. The oligomer lobes capped at the sides of the Au NP can also function as a protection agent for anisotropic photochemical growth of Au NPs, which evolve into Au nanorods and mushrooms with controlled irradiation time. Such polarization-directed etching of oligomer shells has unique advantages of high local-selectivity, controllability, and versatility for on-chip nanofabrication, which opens many new opportunities for integrated nanophotonic devices.

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8

Zhang, Jianmin, Baishun Yang, Huiling Zheng, Xiufeng Han, and Yu Yan. "Large magnetic anisotropy and strain induced enhancement of magnetic anisotropy in monolayer TaTe2." Physical Chemistry Chemical Physics 19, no. 35 (2017): 24341–47. http://dx.doi.org/10.1039/c7cp04445c.

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9

Aras, Mehmet, Sümeyra Güler-Kılıç, and Çetin Kılıç. "Enhancement of the magnetic anisotropy in single semiconductor nanowires via surface doping and adatom deposition." Nanotechnology 33, no. 20 (February 21, 2022): 205202. http://dx.doi.org/10.1088/1361-6528/ac50f0.

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Abstract The magnetic anisotropy of single semiconductor (ZnO and GaN) nanowires incorporating both a transition metal (Co and Mn, respectively) as a substitutional surface dopant and a heavy metal (Au, Bi, or Pt) adatom is studied by performing density-functional supercell calculations with the Hubbard U correction. It is found that a substantial enhancement in the magnetic anisotropy energy is obtained through the deposition of Bi; the deposition of Au and Pt leads to significant variation in other magnetic properties, but not in the magnetic anisotropy energy. An analysis within a band description shows that the coexistence of Bi adatom and a surface dopant with large spin moment activates a mechanism involving reorientation and readjustment of the spin moments of electrons in occupied bands in response to the change of magnetization direction, which promotes giant magnetic anisotropy. Our results for adsorption energetics indicate that the accommodation of Bi in the neighborhood of the surface dopant is more likely in GaN nanowires, because the Bi adatom does (not) tend to be closer to the Mn (Co) dopant on the surface of GaN (ZnO) nanowire. The stability of GaN nanowire with giant magnetic anisotropy owing to the incorporation of both Mn and Bi is demonstrated by performing ab initio molecular dynamics simulations at temperatures considerably higher than room temperature. These results suggest that adatom deposition and surface doping can be used complementarily to develop single nanowire-based spintronic devices.

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10

Shern, C. S., C. W. Su, Y. E. Wu, and S. H. Chen. "Ag induced enhancement of perpendicular magnetic anisotropy." Surface Science 495, no. 3 (December 2001): L821—L826. http://dx.doi.org/10.1016/s0039-6028(01)01610-7.

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11

Anyfantis, Dimitrios I., Nikos Kanistras, Camillo Ballani, Alexandros Barnasas, Vassilios Kapaklis, Georg Schmidt, Evangelos Th Papaioannou, and Panagiotis Poulopoulos. "Magnetic Aspects and Large Exchange Bias of Ni0.9Co0.1/NiCoO Multilayers." Micro 1, no. 1 (July 2, 2021): 43–54. http://dx.doi.org/10.3390/micro1010005.

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Ultrathin films of Ni0.9Co0.1 were grown by radio frequency magnetron sputtering. By means of a periodic natural oxidation procedure they were transformed into Ni0.9Co0.1/NiCoO multilayers. Room temperature hysteresis loops recorded via the magneto-optic Kerr effect have revealed over all in-plane magnetic anisotropy due to magnetostatic anisotropy. Mild thermal annealing at 250 °C enhanced a tendency for perpendicular magnetic anisotropy, mainly due to an increase of the uniaxial volume anisotropy term. Spin reorientation transition, exchange bias larger than 700 Oe, and strong coercivity enhancement were observed via a superconducting quantum interference device at low temperatures after field cooling.

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12

Lee, A.-Young, Ki Hoon Kang, Hyungju Ahn, Jun Hee Han, Min-Ha Lee, and Jong-Woo Kim. "Enhancement of magnetocaloric properties by control of magnetocrystalline anisotropy in Ge doped MnFeHfPSi alloy." AIP Advances 12, no. 9 (September 1, 2022): 095323. http://dx.doi.org/10.1063/5.0102522.

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This study investigated the improvement in magnetocaloric properties with magnetocrystalline anisotropy by Ge doping in MnFeHfPSi alloys. The maximum magnetic entropy change gets larger in alloys with higher magnetocrystalline anisotropy. This result is induced by the fractions of easy and hard magnetization planes. In addition, the magnetocaloric properties indicate large differences based on the direction between the easy magnetization plane and the applied magnetic field. Especially, the difference in magnetic entropy change under a low magnetic field is higher than that under a strong magnetic field. Besides, when magnetic transition occurs from a ferromagnetic to a paramagnetic state, the fraction of the easy magnetization plane decreases. Therefore, orientations with an easy magnetization plane play an important role in the enhancement of magnetocaloric properties.

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13

Ziółkowski, Grzegorz, Dariusz Chrobak, Grażyna Chełkowska, Ondrej Zivotsky, and Artur Chrobak. "Enhancement of Hard Magnetic Properties in Fraktal-Like Nano and Mesoscopic Grains." Materials 14, no. 6 (March 16, 2021): 1443. http://dx.doi.org/10.3390/ma14061443.

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The paper refers to Monte Carlo magnetic simulations for fractal-like nano and mesoscopic grains. The analyzed objects differed in the size, surface development, magnetic anisotropy and the spin values attributed to the system nodes inside the fractal. Such an approach allowed us to determine their magnetization processes as well as optimization characteristics in the direction to enhancement of hard magnetic properties. As it was shown, the size effects depend on the chosen value of magnetic anisotropy. In the case of fractals with ultra-high coercivity, the decreasing of their size leads to deterioration of coercivity, especially for the high surface to volume ratio. Opposite effects were observed for soft magnetic fractals when the nanostructure caused an appearance of the coercive field, and the maximum of energy product was predictably significantly higher than for conventional rare earths’ free permanent magnets.

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14

Liu, Guang, Liwen Zhang, Yang Gan, Yan Wang, Dengke Chen, Yuguo Dai, Lin Feng, Pengfei Zhang, and Huawei Chen. "Liquid transport with direction guidance and speed enhancement from gradient and magnetized micro-cilia surface." Applied Physics Letters 120, no. 19 (May 9, 2022): 191603. http://dx.doi.org/10.1063/5.0089149.

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Liquid transport regulation has attracted wide attention recently due to its potential applications in micro-fluidic devices, heat management, and mechanical engineering. Various liquid regulation strategies for direction guiding and speed enhancing have been developed with inspirations from nature, such as desert beetles and Nepenthes alata peristome with either gradient wettability or anisotropic structures, whereas their combined strategies for enhanced liquid regulations have barely been discussed due to the unclear coupling mechanisms. Herein, inspired by liquid transporting structure on Ligia exotica's leg, a smart flexible surface with gradient distributed and magnetized micro-cilia array is proposed to realize liquid spreading regulations in speed and direction. Different gradients and magnetic fields have been compared for liquid regulating performances, where the anisotropy ratio of liquid spreading could be enhanced from 0 on uniform surface to ∼0.3 on gradients surface, to even ∼0.6 by coupling magnetic field. The underlying liquid regulating mechanism has been established based on the mutual effects of liquid pinning and capillarity at different cilium inclined angles, cilium gap distance, and surface wettability. Finally, several liquid regulation applications are explored and offer potentials for fields of medicine and heat management.

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15

Kelly K. Dobson, Kelly K. Dobson, Wei Jia Wei Jia, and and Ting-Chung Poon and Ting-Chung Poon. "Anisotropic edge enhancement in optical scanning holography with spiral phase filtering." Chinese Optics Letters 14, no. 1 (2016): 010006–10010. http://dx.doi.org/10.3788/col201614.010006.

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16

FIDDY, M. A., R. P. INGEL, and J. O. SCHENK. "ANISOTROPIC METAMATERIALS FOR FIELD ENHANCEMENT AND NEGATIVE INDEX APPLICATIONS." Journal of Nonlinear Optical Physics & Materials 17, no. 04 (December 2008): 357–66. http://dx.doi.org/10.1142/s0218863508004275.

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1D highly anisotropic periodic structures can exhibit very large internal field enhancements and positive spectral phase slopes. The field enhancement can lead to significant external fields radiating from the structure close to frequencies at which the spectral phase slope changes sign and where an effective negative index regime can occur.

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17

Zhao, Hui-Jun, Fei Fan, Tian-Rui Zhang, Yun-Yun Ji, and Sheng-Jiang Chang. "Dynamic terahertz anisotropy and chirality enhancement in liquid-crystal anisotropic dielectric metasurfaces." Photonics Research 10, no. 4 (March 29, 2022): 1097. http://dx.doi.org/10.1364/prj.453082.

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18

Ning, Keyu, Houfang Liu, Linsen Li, Huanglong Li, Jiafeng Feng, Baishun Yang, Xiao Liu, et al. "Tailoring perpendicular magnetic anisotropy with graphene oxide membranes." RSC Advances 7, no. 83 (2017): 52938–44. http://dx.doi.org/10.1039/c7ra08644j.

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19

Khadra, Ghassan, Alexandre Tamion, Florent Tornus, Bruno Canut, and Veronique Dupuis. "Anisotropy in FeCo Nanoparticles, a First Step." Solid State Phenomena 233-234 (July 2015): 550–53. http://dx.doi.org/10.4028/www.scientific.net/ssp.233-234.550.

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In this article, we study the intrinsic magnetic properties of diluted FeCo clusters nanoparticles embedded in an inert amorphous carbon matrix. We report an enhancement of the magnetic anisotropy energy (MAE) after annealing demonstrated by superconducting quantum interference device (SQUID) measurements and adjustments. Rutherford backscattering spectrometry (RBS) was used to quantify the sample stoichiometry and concentration.

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20

Zhang, Luran, Dandan Gao, Huan Liu, Jiyang Xie, and Wanbiao Hu. "Marked Enhancement of Roll-Off Frequency in FeCoN Synthetic Antiferromagnetic Films Deposited by Oblique Incidence." Materials 12, no. 14 (July 22, 2019): 2328. http://dx.doi.org/10.3390/ma12142328.

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A series of FeCoN films were successfully deposited on glass substrates in a magnetron sputtering system. Using oblique incidence method and FeCoN/Ru/FeCoN synthetic antiferromagnetic (SAF) structure, two additional anisotropies energy were introduced: oblique incidence anisotropy and exchange anisotropy energy, which marked enhancement of the effective magnetic anisotropy (Hk). The increment of Hk results in a significant improvement in the roll-off frequency of these films. The roll-off frequency of FeCoN/Ru/FeCoN films with SAF structure can reach up to 8.6 GHz. A feasible approach to conveniently controlling Hk of soft magnetic thin films by using oblique deposition and SAF structure can further improve their properties for the potential applications in the high frequency region.

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21

Гололобов, Петр, Peter Gololobov, Прокопий Кривошапкин, Prokopy Krivoshapkin, Гермоген Крымский, Germogen Krymsky, Владислав Григорьев, Vladislav Grigoryev, Сардаана Герасимова, and Sardaana Gerasimova. "Distribution of tensor anisotropy of cosmic rays near the neutral current sheet." Solar-Terrestrial Physics 3, no. 2 (August 9, 2017): 16–19. http://dx.doi.org/10.12737/stp-3220173.

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We analyze time profiles of isotropic intensity, components of vector and tensor anisotropies of cos-mic rays (CR) when Earth crosses the neutral sheet of the interplanetary magnetic field (IMF) in solar activity cycles 23–24. The moments of the crossings are de-termined from Wilcox Observatory synoptic charts and IMF data. Periods of Forbush decreases and ground level enhancements are excluded from the analysis. The events are analyzed for the epochs of positive and negative signs of the Sun’s general magnetic field. During each epoch, the crossings from the positive sector to the negative one and vice versa are separated. In total, 213 crossing events have been selected. The first two spherical harmonics of the angular CR-distribution are obtained using the global survey method. In each case, the average number of stations is equal to 32. The analysis shows that the temporal change of the isotropic component is caused by a magnetic mirror. For the first time, the zonal harmonics are reliably distinguished, and the existence of the antisymmetric diurnal CR-variation in a low energy range, which is oriented along IMF, is recognized. We compare our results with those obtained earlier.

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22

Peterson, Thomas J., Anthony Hurben, Wei Jiang, Delin Zhang, Brandon Zink, Yu-Chia Chen, Yihong Fan, Tony Low, and Jian-Ping Wang. "Enhancement of voltage controlled magnetic anisotropy (VCMA) through electron depletion." Journal of Applied Physics 131, no. 15 (April 21, 2022): 153904. http://dx.doi.org/10.1063/5.0086768.

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Recent advancement in the switching of perpendicular magnetic tunnel junctions with an electric field has been a milestone for realizing ultra-low energy memory and computing devices. To integrate with current spin-transfer torque-magnetic tunnel junction and spin–orbit torque-magnetic tunnel junction devices, the typical linear fJ/V m range voltage controlled magnetic anisotropy (VCMA) needs to be significantly enhanced with approaches that include new materials or stack engineering. A possible bidirectional and 1.1 pJ/V m VCMA effect has been predicted by using heavily electron-depleted Fe/MgO interfaces. To improve upon existing VCMA technology, we have proposed inserting high work function materials underneath the magnetic layer. This will deplete electrons from the magnetic layer biasing the gating window into the electron-depleted regime, where the pJ/V m and bidirectional VCMA effect was predicted. We have demonstrated tunable control of the Ta/Pd(x)/Ta underlayer's work function. By varying the Pd thickness (x) from 0 to 10 nm, we have observed a tunable change in the Ta layer's work function from 4.32 to 4.90 eV. To investigate the extent of the electron depletion as a function of the Pd thickness in the underlayer, we have performed DFT calculations on supercells of Ta/Pd(x)/Ta/CoFe/MgO, which demonstrate that electron depletion will not be fully screened at the CoFe/MgO interface. Gated pillar devices with Hall cross geometries were fabricated and tested to extract the anisotropy change as a function of applied gate voltage for samples with various Pd thicknesses. The electron-depleted Pd samples show three to six times VCMA improvement compared to the electron accumulated Ta control sample.

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23

Mapley, Martin Christopher, Geoff Tansley, Jo P. Pauls, Shaun D. Gregory, and Andrew Busch. "Selective laser sintering of bonded anisotropic permanent magnets using an in situ alignment fixture." Rapid Prototyping Journal 27, no. 4 (March 29, 2021): 735–40. http://dx.doi.org/10.1108/rpj-09-2020-0220.

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Purpose Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density. Design/methodology/approach Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser. Findings Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field. Originality/value A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.

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24

Gawas, Satu G., Sher Singh Meena, Seikh M. Yusuf, and Vidhyadatta M. S. Verenkar. "Anisotropy and domain state dependent enhancement of single domain ferrimagnetism in cobalt substituted Ni–Zn ferrites." New Journal of Chemistry 40, no. 11 (2016): 9275–84. http://dx.doi.org/10.1039/c6nj02121b.

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Reluctance and favorable orientation of magnetic domain with the field at RT and blocking temperature (T_B), respectively, as an effect of enhanced magnetic anisotropy by virtue of Co substitution.

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25

Kossak, Alexander E., Daniel Wolf, and Geoffrey S. D. Beach. "Magneto-ionic enhancement and control of perpendicular magnetic anisotropy." Applied Physics Letters 121, no. 22 (November 28, 2022): 222402. http://dx.doi.org/10.1063/5.0121767.

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Magneto-ionic control of magnetic anisotropy is an emerging voltage-controlled approach that aims to offer much lower power consumption than current-controlled manipulation of magnetization. Moreover, magneto-ionic systems are ideal candidates for non von Neumann computing architectures, such as neuromorphic and stochastic computing due to their non-volatile and analog nature. One of the key metrics to quantify the efficiency of voltage-controlled magnetic anisotropy (VCMA) is the magneto-electric voltage coefficient ([Formula: see text]). Here, we show greater than one order of magnitude improvement in this efficiency compared to existing solid-state systems using a Co/Pd multilayer heterostructure. By performing a systematic study of the Co thickness, the Pd thickness, and the number of repeat units of engineered Co/Pd multilayers, we identify a narrow bandwidth of the Co thickness from 2–2.5 Å, Pd thickness from 1.4–1.7 nm, and repeat units from 7–9, to maximize the VCMA. Compared to rivaled liquid electrolyte systems, this platform has the advantage of faster speeds and easier integration for on-chip logic and memory devices.

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26

Hajra, Partha, Pradip Brahma, Saurav Dutta, Sourish Banerjee, and Dipankar Chakravorty. "Enhancement of magnetic anisotropy in mechanically attrited Cr2O3 nanoparticles." Journal of Magnetism and Magnetic Materials 324, no. 7 (April 2012): 1425–30. http://dx.doi.org/10.1016/j.jmmm.2011.11.064.

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27

Zhu, Jian-Wei, Xiao-Xiong Wang, Chao Song, Qi Liu, Jin-Xia Sui, Hong-Di Zhang, and Yun-Ze Long. "Magnetic anisotropy and magnetization enhancement of Gd3+-doped SmFeO3." Journal of Magnetism and Magnetic Materials 476 (April 2019): 568–73. http://dx.doi.org/10.1016/j.jmmm.2018.12.106.

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28

Deng, Hui-Hong, and De-Fu Bu. "Hot Accretion Flow in Two-Dimensional Spherical Coordinates: Considering Pressure Anisotropy and Magnetic Field." Universe 5, no. 9 (September 12, 2019): 197. http://dx.doi.org/10.3390/universe5090197.

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For systems with extremely low accretion rate, such as Galactic Center Sgr A* and M87 galaxy, the ion collisional mean free path can be considerably larger than its Larmor radius. In this case, the gas pressure is anisotropic to magnetic field lines. In this paper, we pay attention to how the properties of outflow change with the strength of anisotropic pressure and the magnetic field. We use an anisotropic viscosity to model the anisotropic pressure. We solve the two-dimensional magnetohydrodynamic (MHD) equations in spherical coordinates and assume that the accretion flow is radially self-similar. We find that the work done by anisotropic pressure can heat the accretion flow. The gas temperature is heightened when anisotropic stress is included. The outflow velocity increases with the enhancement of strength of the anisotropic force. The Bernoulli parameter does not change much when anisotropic pressure is involved. However, we find that the energy flux of outflow can be increased by a factor of 20 in the presence of anisotropic stress. We find strong wind (the mass outflow is about 70% of the mass inflow rate) is formed when a relatively strong magnetic field is present. Outflows from an active galactic nucleus can interact with gas in its host galaxies. Our result predicts that outflow feedback effects can be enhanced significantly when anisotropic pressure and a relatively powerful magnetic field is considered.

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Zhou, Shanhu, and Jun Hu. "Enhancing perpendicular magnetocrystalline anisotropy in Fe ultrathin films by non-noble transition-metal substrate." International Journal of Modern Physics C 31, no. 09 (August 27, 2020): 2050134. http://dx.doi.org/10.1142/s012918312050134x.

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Based on first-principles calculations, we studied the magnetic properties of ultrathin Fe film on a nonmagnetic substrate Ta(001). We found that the perpendicular magnetocrystalline anisotropy (PMA) of Fe/Ta(001) system with only one or two Fe atomic layer(s) can be enhanced significantly, and the corresponding magnetocrystalline anisotropy energy is enlarged tos about 3 times of that in pure ultrathin Fe film. Analysis of electronic properties demonstrates that the magnetic proximity effect at the Fe/Ta interface plays an important role in the enhancement of the PMA. Alternative arrangement of Ta and Fe layers with more Fe/Ta interfaces may further strengthen the PMA.

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Karolus, Małgorzata. "Structural Studies of the Relaxed Amorphous Phase in the Fe₈₁B₁₄Nb₅ Alloy." Solid State Phenomena 203-204 (June 2013): 380–85. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.380.

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Amorphous alloys based on iron, obtained by melt spinning technique, are modern and very promising soft magnetic materials. The thermal annealing at temperatures closed to the crystallization temperature can cause an increase of magnetic permeability more than 10 times i.e. the so called enhancement of soft magnetic properties effect (ESMP). It is usually explained by formation of iron nanocrystallites in amorphous surroundings or by formation of the relaxed amorphous phase. Such a microstructure leads to averaging out of magnetic anisotropy and cause the ESMP.

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31

Chen, S. C., Po Cheng Kuo, Chih Long Shen, Y. H. Fang, K. T. Huang, and G. P. Lin. "Microstructures and Magnetic Properties of Nanocomposite FePt Multilayer Films." Advanced Materials Research 47-50 (June 2008): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.579.

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Sputter-deposited FePt films exhibit an in-plane magnetic anisotropy when they use MgO as capped layer. The perpendicular magnetic anisotropy of FePt films are enhanced by introducing Ag capped layer instead of MgO capped layer. Although the in-plane coercivity (Hc⊥ ) of FePt films decreases slightly after introducing an Ag capper layer instead of a MgO capped layer, the perpendicular coercivity (Hc⊥ ) is increased significantly from 3169 Oe to 6726 Oe. The Auger electron spectroscopy analysis confirms that the Ag atoms diffuse from capped layer into the FePt magnetic layer and the Ag atoms mainly distribute at the grain boundary of FePt. This phenomenon results in the grain boundary energy enhancement and the grain growth inhibition and therefore increases the perpendicular coercivity and decrease the grain size of the FePt film.

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32

Schulz, N., A. Chanda, G. Datt, M. Venkata Kamalakar, T. Sarkar, M. H. Phan, and H. Srikanth. "Proximity enhanced magnetism at NiFe₂O₄/Graphene interface." AIP Advances 12, no. 3 (March 1, 2022): 035132. http://dx.doi.org/10.1063/9.0000271.

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Here, we explore the change in effective magnetic anisotropy of the ferrimagnetic (FM) insulator nickel ferrite (NFO) thin film due to the inclusion of monolayer graphene (MLG) grown on top of the NFO layer. This was done by performing radio frequency (RF) transverse susceptibility (TS) measurements on bare NFO and NFO/MLG bilayer samples for both in-plane (IP) and out-of-plane (OOP) configurations utilizing a tunnel diode oscillator technique. Our magnetometry measurements indicated an enhancement in the overall saturation magnetization of the NFO/MLG bilayer with respect to the bare NFO film. The TS measurements reveal that the inclusion of MLG reduces the effective magnetic anisotropy for both IP and OOP configurations drastically, by up to a factor of 2 over the temperature range 40 K ≤ T ≤ 280 K. Since NFO is a magnetic substrate, it is possible that NFO could induce magnetic ordering in MLG at the NFO/MLG interface via the magnetic proximity effect. Furthermore, since NFO is insulating and MLG is a semimetal, there likely exists a large conductivity difference at the interface, making charge transfer plausible. These two effects could modify the interfacial magnetism leading to a change in the effective magnetic anisotropy. These results highlight the importance of understanding the interfacial magnetism of FM/MLG heterostructures.

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33

González, J. M., N. Murillo, J. González, J. M. Blanco, and J. Echeberría. "On the intergranular coupling in soft nanocrystalline materials." Journal of Materials Research 11, no. 2 (February 1996): 512–17. http://dx.doi.org/10.1557/jmr.1996.0061.

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The magnetic softness of nanocrystalline materials prepared from amorphous precursors is attributed to the average of the local magnetocrystalline anisotropy of the individual crystallites. In the present paper we have studied the effective magnetic anisotropy of Fe-based nanocrystalline samples with different microstructures. These microstructures were produced by using different heating rates when crystallizing the precursor material by means of continuous heating treatments. From the results of our study of the magnetic properties of the samples, carried out from the measurement of the bias field dependence of the transverse susceptibility, it was possible to discern the occurrence of intergranular coupling and to evaluate the typical dimensions of the coupled units. Since these dimensions were larger than the characteristic length of the microstructure, we suggest that the enhancement of the soft properties is linked to the decrease of the microstructure-magnetization interactions originating in large units of coupled magnetic moments.

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34

Liu, Shan-Shan, Ke Lang, Yi-Quan Zhang, Qian Yang, Bing-Wu Wang, and Song Gao. "A distinct magnetic anisotropy enhancement in mononuclear dysprosium–sulfur complexes by controlling the Dy-ligand bond length." Dalton Transactions 45, no. 19 (2016): 8149–53. http://dx.doi.org/10.1039/c6dt01089j.

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A significant enhancement of magnetic anisotropy is achieved by replacing two of the S-based ligands of a field-induced SIM [(dtc)₃Dy(phen)] with O-based ligands, dbm⁻ ligands, yielding a rarely reported sulfur-ligated Ln–SIM [(dbm)₂Dy(dtc)(phen)].

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35

Grigorenko, Elena E., Andrey Y. Malykhin, Elena A. Kronberg, and Evgeny V. Panov. "Quasi-parallel Whistler Waves and Their Interaction with Resonant Electrons during High-velocity Bulk Flows in the Earth’s Magnetotail." Astrophysical Journal 943, no. 2 (February 1, 2023): 169. http://dx.doi.org/10.3847/1538-4357/acaf52.

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Abstract In collisionless space, plasma waves are important channels of energy conversion, affecting the local particle velocity distribution functions through wave–particle interactions. In this paper we present a comparative statistical analysis of the characteristics of quasi-parallel narrowband whistler waves and the properties of resonant electrons interacting with these waves during the intervals of earthward and tailward high-velocity bulk flows produced by the near-Earth X-line and observed by Magnetospheric Multiscale Mission spacecraft. We found that on both sides of the X-line, the suprathermal electrons (≥1 keV) having large pitch angles make the major contribution to the maximal growth rate (γ) of these waves. The whistler waves were observed almost simultaneously with strong enhancements of perpendicular magnetic gradients localized at electron scales near dipolarization fronts associated with the earthward bulk flows, and near flux ropes/magnetic islands embedded into the tailward bulk flows. Betatron energization of electrons due to the appearance of such gradients increases the perpendicular anisotropy of electron distribution, which could be responsible for the whistler wave generation. We found that in the course of electron interactions with the whistler waves the lower-energy resonant electrons can transfer a part of their kinetic energy to the higher-energy electrons, especially in the Central Plasma Sheet. This results in formation/enhancement of energy-dependent perpendicular anisotropy and power-law tails in the high-energy range of electron velocity distribution. We conclude that despite the differences in the magnetic structure of the earthward and tailward bulk flows, the mechanisms of the quasi-parallel whistler wave generation and the properties of resonant electrons are quite similar.

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36

Norouzi-Inallu, M., P. Kameli, A. Ghotbi Varzaneh, I. Abdolhosseini Sarsari, M. Abbasi Eskandari, I. Orue, B. Rodríguez-Crespo, and V. Chernenko. "Influence of W doping on the structure, magnetism and exchange bias in Ni₄₇Mn₄₀Sn_{13− x}W_x Heusler alloys." Journal of Physics: Condensed Matter 34, no. 22 (March 31, 2022): 225803. http://dx.doi.org/10.1088/1361-648x/ac5311.

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Abstract The influence of the W-doping on the martensitic transformation, magnetic properties and exchange bias (EB) effect in the Ni47Mn40Sn13−x W x (x = 0, 0.5, 1, 1.25 at.%) magnetic shape memory alloys has been investigated. It is found that the W-doping causes a simultaneous reduction of both the ferromagnetic (FM) exchange coupling and enhancement of the magnetic anisotropy, leading to a decrease of the magnetic moment of the low-temperature phase and to a higher attainable EB. The magnetic memory measurements reveal the presence of a glassy magnetic ground state, which can significantly impact the reduction of magnetization and enhancement of EB in the studied bulk alloys. It is argued that the glassy magnetic ground state originates from the partial magnetic disorder resulting from the correlation between the antiferromagnetic and FM states. The results demonstrate that the doping by W instead of Sn is an efficient tool to tailor the EB effect in the Ni–Mn–Sn-based Heusler alloys, whereby they are promising for spintronic applications.

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37

Walsh, C. A., S. O'Neill, J. P. Chittenden, A. J. Crilly, B. Appelbe, D. J. Strozzi, D. Ho, et al. "Magnetized ICF implosions: Scaling of temperature and yield enhancement." Physics of Plasmas 29, no. 4 (April 2022): 042701. http://dx.doi.org/10.1063/5.0081915.

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This paper investigates the impact of an applied magnetic field on the yield and hot-spot temperature of inertial confinement fusion implosions. A scaling of temperature amplification due to magnetization is shown to be in agreement with unperturbed two-dimensional (2D) extended-magnetohydrodynamic simulations. A perfectly spherical hot-spot with an axial magnetic field is predicted to have a maximum temperature amplification of 37%. However, elongation of the hot-spot along field lines raises this value by decreasing the hot-spot surface area along magnetic field lines. A scaling for yield amplification predicts that a magnetic field has the greatest benefit for low-temperature implosions; this is in agreement with simplified 1D simulations, but not 2D simulations where the hot-spot pressure can be significantly reduced by heat-flow anisotropy. Simulations including a P2 drive asymmetry then show that the magnetized yield is a maximum when the capsule drive corrects the hot-spot shape to be round at neutron bang time. An applied magnetic field is also found to be most beneficial for implosions that are more highly perturbed, exceeding the theoretical yield enhancement for symmetric hot-spots. Increasing the magnetic field strength past the value required to magnetize the electrons is beneficial due to the additional suppression of perturbations by magnetic tension.

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38

Pearson, Tyler J., Majed S. Fataftah, and Danna E. Freedman. "Enhancement of magnetic anisotropy in a Mn–Bi heterobimetallic complex." Chemical Communications 52, no. 76 (2016): 11394–97. http://dx.doi.org/10.1039/c6cc06369a.

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39

Okamoto, Satoshi, Osamu Kitakami, and Yutaka Shimada. "Enhancement of magnetic anisotropy of hydrogenated Pd/Co/Pd trilayers." Journal of Magnetism and Magnetic Materials 239, no. 1-3 (February 2002): 313–15. http://dx.doi.org/10.1016/s0304-8853(01)00596-0.

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40

Şimşek, Telem, and Şadan Özcan. "Effective magnetic anisotropy enhancement of FePt nanocrystals through shape control." Journal of Magnetism and Magnetic Materials 351 (February 2014): 47–51. http://dx.doi.org/10.1016/j.jmmm.2013.09.051.

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41

Islam, M. Fhokrul, and Shiv N. Khanna. "On the enhancement of magnetic anisotropy in cobalt clusters via non-magnetic doping." Journal of Physics: Condensed Matter 26, no. 12 (March 6, 2014): 125303. http://dx.doi.org/10.1088/0953-8984/26/12/125303.

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42

Yu, Ying, Shu Hong Xie, and Qing Feng Zhan. "Effect of Thickness on Mechanically Tunable Magnetic Anisotropy of FeGa Thin Films Deposited on Flexible Substrates." Materials Science Forum 815 (March 2015): 227–32. http://dx.doi.org/10.4028/www.scientific.net/msf.815.227.

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A practical way to manipulate the magnetic anisotropy of magnetostrictive FeGa thin films grown on flexible polyethylene terephthalate (PET) substrates is introduced in this study. The effect of film thickness on magnetic properties and magnetostriction constant of polycrystalline FeGa thin films was investigated. The anisotropy field Hk of flexible FeGa films, i.e., the saturation field determined by fitting the hysteresis curves measured along the hard axis, was enhanced with increasing the tensile strain applied along the easy axis of the thin films, but this enhancement via strain became unconspicuous with increasing the thickness of FeGa films. In order to study the magnetic sensitivity of thin films responding to the external stress, we applied different strains on these films and measure the corresponding anisotropy field. Moreover, the effective magnetostriction constant of FeGa films was calculated from the changes of both anisotropy field and external strain based on the Villari effect. A Neel’s phenomenological model was developed to illustrate that the effective anisotropy field of FeGa thin films was contributed from both the constant volume term and the inverse thickness dependent surface term. Therefore, the magnetic properties for the volume and surface of FeGa thin films were different, which has been verified in this work by using vibrating sample magnetometer (VSM) and magneto-optic Kerr effect (MOKE) system. The anisotropy field contributed by the surface of FeGa film and obtained by MOKE is smaller than that contributed by the film volume and measured by VSM. We ascribed the difference in Hk to the relaxation of the effective strain applied on the films with increasing the thickness of films.

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43

Salaheldeen, Mohamed, Ayman Nafady, Ahmed M. Abu-Dief, Rosario Díaz Crespo, María Paz Fernández-García, Juan Pedro Andrés, Ricardo López Antón, Jesús A. Blanco, and Pablo Álvarez-Alonso. "Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size." Nanomaterials 12, no. 15 (July 24, 2022): 2544. http://dx.doi.org/10.3390/nano12152544.

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The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.

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Korobova, Julia, Dmitry Bazhanov, and Irina Kamynina. "Oxygen Effect on Magnetic Anisotropy Energy of Co Nanowires on Cu(210) Surface - An Ab Initio Study." Solid State Phenomena 233-234 (July 2015): 530–33. http://dx.doi.org/10.4028/www.scientific.net/ssp.233-234.530.

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An ab initio study of Co monatomic nanowires (NW) magnetic properties on pure and oxygen reconstructed Cu (210) surface was performed. Strong influence of oxygen surface impurity on MAE in Co nanowire was found. High value of magnetic moment and small energy of magnetic anisotropy (MAE) were obtained in Co nanowires on pure Cu (210) surface. After oxygen reconstruction of Cu (210) surface (Cu (210)-(2×1)O) the significant enhancement of MAE was found in Co nanowires, while the magnetic moment of Co atoms is practically unchanged. Oxygen on Cu (210) surface rotates easy magnetization axis in Co NW with respect to the pure surface.

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45

Song, M. Y., G. Y. Luo, J. G. Lin, M. G. Samant, and S. S. P. Parkin. "Influence of Magnetic Anisotropy on Inverse Spin Hall Voltage." SPIN 07, no. 04 (December 2017): 1750007. http://dx.doi.org/10.1142/s2010324717500072.

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Spin pumping efficiency (SPE) in a ferromagnetic (FM)/Pt system relies on the effective magnetization damping of FM layer and the interface spin mixing conductance. However, there are very few studies on the influence of magnetic anisotropy of FM material on SPE. In this study, the spin pumping induced spin voltage [Formula: see text] in Fe3O4(58.9[Formula: see text]nm)/Pt(5.5[Formula: see text]nm) is investigated in two different orientations of the external magnetic field, one parallel and other perpendicular to the in-plane easy axis of Fe3O4. The value of [Formula: see text] with the magnetic field along the easy axis is 38% higher compared with that along the hard axis. The possible origin of this enhancement is investigated based on the model of ferromagnetic resonance induced spin pumping.

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46

Londoño Navarro, Juanita, Juan Carlos Riaño-Rojas, and Elisabeth Restrepo-Parra. "Competition between anisotropy and dipolar interaction in multicore nanoparticles: Monte Carlo simulation." DYNA 82, no. 194 (December 21, 2015): 66–71. http://dx.doi.org/10.15446/dyna.v82n194.44297.

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Monte Carlo simulations combined with the Heisenberg model and Metropolis algorithm were used to study the equilibrium magnetic properties of magnetic multi-core nanoparticles of magnetite. Three effects were considered in this simulation: the Zeeman effect, magneto crystalline anisotropy, and dipolar interaction. Moreover, the influence of the size distribution (mean diameter and standard deviation) on the magnetization was analyzed. As an important result, a reduction of the equilibrium magnetization caused by the dipolar interaction and the magneto crystalline anisotropy was observed. On the other hand, the nanoparticle size increase produces an enhancement in the equilibrium magnetization, because of the lower influence of dipolar interaction. Cooling temperature effect was also observed, presenting a decrease in the equilibrium magnetization as the temperature was increased. The influence of the easy axis direction was studied.

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47

Chipara, Mircea, Tom George, Yingfan Xu, Ralph Skomski, Lanping Yue, Nasar Ali, and David J. Sellmyer. "Magnetism of FePt Nanoclusters in Polyimide." Journal of Nanomaterials 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/587847.

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FePt nanoclusters have been implanted onto polyimide films and subjected to thermal annealing in order to obtain a special magnetic phase (L10) dispersed within the polymer. SQUID measurements quantified the magnetic features of the as-prepared and annealed hybrid films. As-implanted FePt nanoparticles in polyimide films exhibited a blocking temperature of 70 ± 5 K. Thermal annealing in zero and 10 kOe applied magnetic field increased the magnetic anisotropy and coercivity of the samples. Wide Angle X-Ray Scattering confirmed the presence of FePt and L10phase. All samples (as deposited and annealed) exhibited electron spin resonance spectra consisting of two overlapping lines. The broad line was a ferromagnetic resonance originating from FePt nanoparticles. Its angular dependence indicated the magnetic anisotropy of FePt nanoparticles. SEM micrographs suggest a negligible coalescence of FePt nanoparticles, supporting that the enhancement of the magnetic properties is a consequence of the improvement of the L10structure. The narrow ESR line was assigned to nonmagnetic (paramagnetic) impurities within the samples consistent with graphite-like structures generated by the local degradation of the polymer during implantation and annealing. Raman spectroscopy confirmed the formation of graphitic structures in annealed KHN and in KHN-FePt.

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48

Yao, Y., S. F. Liu, K. E. Zhu, W. Kong, J. Q. Li, and J. Q. Dong. "TEM in toroidal plasmas with anisotropic electron temperature." Nuclear Fusion 62, no. 3 (February 3, 2022): 036027. http://dx.doi.org/10.1088/1741-4326/ac3e3d.

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Abstract Trapped electron modes (TEMs) in tokamak plasmas with anisotropies of electron temperature and its gradient are studied by solving the gyrokinetic integral eigenmode equation. Detailed numerical analyses indicate that, in comparison with that in plasmas of isotropic electron temperature, TEMs are enhanced (weakened) by the anisotropy with temperature in the direction perpendicular to magnetic field higher (lower) than that in the direction parallel to the magnetic field when the latter is kept constant. However, the enhancement is limited such that TEMs are weakened rapidly and even stabilized when the anisotropy is higher than a critical value owing to an effective reduction of bounce movement of the trapped electrons. In addition, it is found that the gradients of perpendicular and parallel temperatures of electrons have driving and suppressing effects on the TEMs, respectively. The overall effects of the temperature gradients of electrons and ions, magnetic shear, safety factor, and density gradient on TEMs in the presence of the anisotropies are presented in detail.

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49

Mohanan, Vaisakh V., Balaram Pradhan, Vimala Sridurai, Channabasaveshwar V. Yelamaggad, Ammathnadu S. Achalkumar, and Geetha G. Nair. "Giant enhancement and facile tuning of photoluminescence in a soft anisotropic magneto-gel." Nanoscale 10, no. 33 (2018): 15686–95. http://dx.doi.org/10.1039/c8nr02725k.

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50

BORGOHAIN, CHANDAN, KULA KAMAL SENAPATI, DEBABRATA MISHRA, ALAGARSAMY PERUMAL, KANAK CHANDRA SARMA, and PRODEEP PHUKAN. "MICROSTRUCTURAL CHANGES UPON ANNEALING AND IT'S EFFECT ON MAGNETIC AND MECHANICAL PROPERTIES OF NANOSIZED COBALT–FERRITE." International Journal of Nanoscience 11, no. 01 (February 2012): 1250005. http://dx.doi.org/10.1142/s0219581x12500056.

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Nanocrystalline cobalt–ferrite particles of size 20–30 nm have been prepared by a reverse coprecipitation technique under the assistance of ultrasonic irradiation and heat-treatment at different temperatures (from 473 K to 1073 K). Both X-ray diffraction and transmission electron microscope analysis confirms the reduction of strain present in the material with annealing temperature. Enhancement of coercivity and magnetization value has been observed without increase in the particle size for whole range of annealing temperature. Temperature dependent magnetization loop shows considerable magnetic hardening at low temperature. The observed enhancement of the coercivity value has been attributed to the increase in magneto-crystalline anisotropy, surface effects and exchange anisotropy. The mechanical properties of the pure cobalt–ferrite samples and cobalt–ferrite reinforced alumina samples were also examined. The Vickers microhardness and the compressive properties obtained from the stress–strain relation showed higher value with annealing temperatures and higher nanoparticle content.

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