Bibliographies thématiques / Magnetic anisotrophy

Littérature scientifique sur le sujet « Magnetic anisotrophy »

Auteur : Grafiati
Publié le 18 mai 2024

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Articles de revues sur le sujet "Magnetic anisotrophy"

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Hartmann, Tue, Sanne Vandborg, Raben Rosenberg, Leif Sørensen et Poul Videbech. « Increased fractional anisotropy in cerebellum in obsessive–compulsive disorder ». Acta Neuropsychiatrica 28, no 3 (2 novembre 2015) : 141–48. http://dx.doi.org/10.1017/neu.2015.57.

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BackgroundPrevious morphology and diffusion-imaging studies have suggested that structural changes in white matter is an important part of the pathophysiology of obsessive–compulsive disorder (OCD). However, different methodological approaches and the heterogeneity of patient samples question the validity of the findings.Materials and methodsIn total, 30 patients were matched for age and sex with 30 healthy controls. All participants underwent T1-weighted magnetic resonance imaging, diffusion tensor imaging and T2 fluid-attenuated inversion recovery. Voxel-based morphometry and tract-based spatial statistics were used to compare white matter volumes and diffusion tensor imaging between groups. These data were analysed correcting for the effects of multiple comparisons, age, sex, severity and duration of illness as nuisance covariates. White matter hyperintensities were manually identified.ResultsIncrease in fractional anisotropy in cerebellum was the most prominent result. A decrease in fractional anisotrophy in patients comparable with previous studies was located in forceps minor. There were no differences in the white matter morphology or in the white matter hyperintensities between patients and healthy controls.ConclusionDecrease in fractional anisotrophy in forceps minor and increase in cerebellum were found, and they were not due to neither white matter hyperintensities nor morphology of the white matter. Cerebellar hyperconnectivity could be an important part of OCD pathophysiology.
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Soinski, M. « The anisotrophy of coercive force in cold-rolled goss-texture electrical sheets ». IEEE Transactions on Magnetics 23, no 6 (novembre 1987) : 3878–81. http://dx.doi.org/10.1109/tmag.1987.1065769.

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Rongkonusa, Melisa, Gerald Tamuntuan et Guntur Pasau. « Analisis Anisotropi Suseptibilitas Magnetik Batuan Beku Lengan Utara Sulawesi ». Jurnal MIPA 6, no 1 (2 mai 2017) : 8. http://dx.doi.org/10.35799/jm.6.1.2017.15846.

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Telah dilakukan penelitian untuk menentukan pola anisotropi suseptibilitas magnetik dan status singkapan batuan beku dari pola yang diperoleh. Pengukuran anisotropi suseptibilitas magnetic dilakukan pada lima sampel batuan beku dari Sulawesi Utara menggunakan Bartington MS2B. Arah pengukuran sampel disesuaikan dengan desain Tauxe. Hasilnya menunjukkan bahwa suseptibilitas maksimum terdistribusi disekitar arah utara dan timur. Sedangkan suseptibilitas intermediet dan minimum terdistribusi disekitar Utara-Timur dan Timur-Selatan. Elipsoida suseptibilitas cenderung prolate atau lebih lonjong. Batuan beku yang dianalisis merupakan kelompok batuan terobosan yang mekanisme lelehannya terjadi secara vertikal.A research has been conducted to determine the anisotropic pattern of magnetic susceptibility and the status of igneous rocks exposure from the obtained pattern. We have measured the anisotropy of magnetic susceptibility on five samples of igneous rock from North Sulawesi by Bartington MS2B. The position of samples were adjusted according to the Tauxe’s design. The result shows that the maximum susceptibility is distributed around northward and eastward, while the intermediate and minimum susceptibility are distributed around nortward-eastward and eastward-southward. The susceptibility ellipsoid tends to be prolate or more oval. This shows that the igneous rocks that have been analyzed are group of intrusive rocks which melting mechanism occurs through vertical fracture.enetie
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Nauman, Muhammad, Tayyaba Hussain, Joonyoung Choi, Nara Lee, Young Jai Choi, Woun Kang et Younjung Jo. « Low-field magnetic anisotropy of Sr2IrO4 ». Journal of Physics : Condensed Matter 34, no 13 (20 janvier 2022) : 135802. http://dx.doi.org/10.1088/1361-648x/ac484d.

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Abstract Magnetic anisotropy in strontium iridate (Sr2IrO4) is essential because of its strong spin–orbit coupling and crystal field effect. In this paper, we present a detailed mapping of the out-of-plane (OOP) magnetic anisotropy in Sr2IrO4 for different sample orientations using torque magnetometry measurements in the low-magnetic-field region before the isospins are completely ordered. Dominant in-plane anisotropy was identified at low fields, confirming the b axis as an easy magnetization axis. Based on the fitting analysis of the strong uniaxial magnetic anisotropy, we observed that the main anisotropic effect arises from a spin–orbit-coupled magnetic exchange interaction affecting the OOP interaction. The effect of interlayer exchange interaction results in additional anisotropic terms owing to the tilting of the isospins. The results are relevant for understanding OOP magnetic anisotropy and provide a new way to analyze the effects of spin–orbit-coupling and interlayer magnetic exchange interactions. This study provides insight into the understanding of bulk magnetic, magnetotransport, and spintronic behavior on Sr2IrO4 for future studies.
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Maniur, Rafael F., Adam Badra Cahaya et Azwar Manaf. « Law of Approach to Saturation for Determining Magnetic Intrinsic Behavior of BaFe12-xMnx/2Tix/2O19 and SrFe12-xMnx/2Tix/2O19 ». Al-Fiziya : Journal of Materials Science, Geophysics, Instrumentation and Theoretical Physics 4, no 2 (5 janvier 2022) : 78–82. http://dx.doi.org/10.15408/fiziya.v4i2.22206.

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The problem with permanent magnetic materials of very high anisotropic fields is that it is still difficult to determine the intrinsic magnetic properties, when measured using a magnetometer which has a limited magnetic field. The Law of Approach to Saturation (LAS) mathematical model provides a way to measure permanent magnets, with high anisotropic fields by correcting the magnetization data of the first quadrant curve or the virgin curve of the minor hysteresis loop. In this research, a computational LAS program was conducted to compute the intrinsic magnetic properties of magnetic materials, such as saturation magnetization, anisotropy field and magnetocrystalline anisotropy constant. Magnetization data were obtained from permagraph measurements of barium hexaferrite (BaFe12O19), strontium hexaferrite (SrFe12O19) and microwave absorbers BaFe12-xMnx/2Tix/2O19 and SrFe12-xMnx/2Tix/2O19. The convergences of magnetization were assessed to determine the effect of substitution on barium hexaferrite and strontium hexaferrite materials on saturation magnetization values, anisotropy constants and anisotropic fields.
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Deb, Debabrata, Banibrata Mukhopadhyay et Fridolin Weber. « Effects of Anisotropy on Strongly Magnetized Neutron and Strange Quark Stars in General Relativity ». Astrophysical Journal 922, no 2 (26 novembre 2021) : 149. http://dx.doi.org/10.3847/1538-4357/ac222a.

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Abstract We investigate the properties of anisotropic, spherically symmetric compact stars, especially neutron stars (NSs) and strange quark stars (SQSs), made of strongly magnetized matter. The NSs are described by the SLy equation of state (EOS) and the SQSs by an EOS based on the MIT Bag model. The stellar models are based on an a priori assumed density dependence of the magnetic field and thus anisotropy. Our study shows that not only the presence of a strong magnetic field and anisotropy, but also the orientation of the magnetic field itself, have an important influence on the physical properties of stars. Two possible magnetic field orientations are considered: a radial orientation where the local magnetic fields point in the radial direction, and a transverse orientation, where the local magnetic fields are perpendicular to the radial direction. Interestingly, we find that for a transverse orientation of the magnetic field, the stars become more massive with increasing anisotropy and magnetic-field strength and increase in size since the repulsive, effective anisotropic force increases in this case. In the case of a radially oriented magnetic field, however, the masses and radii of the stars decrease with increasing magnetic-field strength because of the decreasing effective anisotropic force. Importantly, we also show that in order to achieve hydrostatic equilibrium configurations of magnetized matter, it is essential to account for both the local anisotropy effects as well as the anisotropy effects caused by a strong magnetic field. Otherwise, hydrostatic equilibrium is not achieved for magnetized stellar models.
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HU, AI-YUAN, et YUAN CHEN. « TWO-DIMENSIONAL ANISOTROPIC HEISENBERG FERROMAGNET IN COEXISTING TRANSVERSE AND LONGITUDINAL MAGNETIC FIELDS ». International Journal of Modern Physics B 21, no 22 (10 septembre 2007) : 3877–87. http://dx.doi.org/10.1142/s0217979207037879.

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The two-dimensional spin-1/2 anisotropic Heisenberg ferromagnet is investigated in coexisting transverse and longitudinal magnetic fields. Using the Green function treatment, the magnetization and susceptibility are studied as a function of temperature, anisotropy and magnetic fields. The effects of exchange anisotropy and transverse magnetic field on the magnetic properties of the system are discussed.
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KRAUS, L. « LOCAL MAGNETIC ANISOTROPY AND MAGNETOANELASTIC EFFECT IN AMORPHOUS AND NANOCRYSTALLINE ALLOYS ». International Journal of Modern Physics B 07, no 01n03 (janvier 1993) : 916–21. http://dx.doi.org/10.1142/s0217979293001979.

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Anelastic deformation of amorphous and nanocrystalline metals results in an anisotropic distribution of atomic pair bonds. This mechanism can lead to rather strong macroscopic magnetic anisotropy in some alloys. Experimental results show that the creep-induced magnetic anisotropy of amorphous and nanocrystalline Fe- and Co-based alloys essentially depends both on TM and metalloid elements. This is a clear evidence that the random local magnetic anisotropy in these materials is closely related to the details of electronic structure. Based on this conclusion a model of bond -orientational anisotropy taking into account the distribution of local anisotropies in TM-based alloys is proposed.
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Min'kova, A. V., V. V. Prudnikov et P. V. Prudnikov. « Issledovanie vliyaniya effektov konkurentsii razlichnykh tipov anizotropii na kriticheskoe povedenie mul'tisloynykh magnitnykh struktur ». Журнал экспериментальной и теоретической физики 164, no 5 (15 décembre 2023) : 782–89. http://dx.doi.org/10.31857/s0044451023110081.

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The influence of the competition of single-ion anisotropy and easy-plane anisotropy on the magnetic properties of the multilayer structure Co/Cu/Co is investigated. The peculiarities of the influence of anisotropy effects are revealed both in the vicinity of critical temperature Tc and in the low-temperature range T Tc. The magnetic properties of the multilayer structure are numerically simulated using the anisotropic Heisenberg model. In the vicinity of Tc, easy-plane anisotropy is shown to exert a predominant influence on the magnetic properties of the structure as compared to the influence of single-ion anisotropy. In the low-temperature range, the switching of the magnetic state of the ferromagnetic film in an external field leads to the appearance of specific features in hysteresis effects due to the competition of two types of magnetic anisotropy. The magnetic structure exhibits a size-induced transition from the behavior caused by easy-plane anisotropy to the behavior caused by single-ion anisotropy. The revealed size-induced transition is accompanied by a spin-flop effect.
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Wang, Hanchen, Yuben Yang, Marco Madami, Yizhan Wang, Mian Du, Jilei Chen, Yu Zhang et al. « Anomalous anisotropic spin-wave propagation in thin manganite films with uniaxial magnetic anisotropy ». Applied Physics Letters 120, no 19 (9 mai 2022) : 192402. http://dx.doi.org/10.1063/5.0088546.

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Manipulation of the spin-wave coherent length is highly desirable to overcome intrinsic damping and to improve functionalities of magnonics materials and devices. In this work, based on angle-resolved propagating spin-wave spectroscopy and micro-focused Brillouin light scattering, we report a giant anisotropy of spin wave propagation in a 20 nm-thick La0.67Sr0.33MnO3 film grown on a NdGaO3 substrate. Vanishing of such anisotropic features in reference experiments where the La0.67Sr0.33MnO3 film is grown on SrTiO3 suggests that the anisotropic spin-wave propagation might be originated from different lattice mismatches of the LSMO film with these two substrates. Interestingly, the decay length and the relaxation time of spin waves are found to be largest when the wavevector is along the [110] crystalline orientation, which is neither at easy nor hard axis related to the in-plane uniaxial magnetic anisotropy. This suggests the possibility of individual control of the magnetic anisotropy and spin-wave anisotropy via strain engineering. Our discovery may enrich the material systems for anisotropic spin wave behavior and promote strain engineering and optimization of versatile magnonic devices.
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Thèses sur le sujet "Magnetic anisotrophy"

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Chuang, Donna Sue. « Magnetic anisotrophy in ultrathin epitaxial films grown on surfaces vicinal to Cu(001) ». Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/32145.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.
Vita.
Includes bibliographical references (leaves 115-119).
by Donna Sue Chuang.
Ph.D.
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Mitra, Mukul Kumar. « Determination of order parameters of liquid crystals from birefringence, x-ray and magnetic anisotrophy studies ». Thesis, University of North Bengal, 1987. http://hdl.handle.net/123456789/822.

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Silva, Rafael Emidio da. « Correspondência histológica de parâmetros de imagens de tensores de difusão ». Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/5/5151/tde-04092014-145000/.

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INTRODUÇÃO: Imagens por tensores de difusão (diffusion tensor imaging - DTI) do cérebro são parte fundamental de exames de ressonância magnética (RM) na rotina clínica. Entretanto, não há informação científica suficiente para inferir a base histológica de parâmetros de imagens de DTI. Um dos achados frequentes nos exames de RM são as áreas de alteração de sinal na substância branca (AASSB). Neste estudo, analisamos imagens de RM post-mortem, em particular as AASSB, e seus correlatos histológicos e imuno-histoquímicos. OBJETIVOS: Descrever os parâmetros quantitativos de imagens de DTI imagens obtidas in cranio post-mortem, comparar com parâmetros de relaxometria e transferência de magnetização e avaliar seus correlatos histológicos nas AASSB e AHAN, utilizando técnicas de correspondência espacial ponto-a-ponto. MÉTODOS: Analisamos áreas distribuídas na substância branca de encéfalos de quatro sujeitos submetidos ao exame de RM post-mortem, aproximadamente 12,87 horas (±2,59). A RM foi realizada em sistema com campo de 3,0 T, sendo utilizadas imagens FLAIR; T2 multi-eco, DTI, Densidade de Prótons para cálculo da taxa de transferência de magnetização (magnetization transfer ratio - MTR). Foram delimitadas regiões de interesse (ROI) em 20 áreas contendo AASSB e 20 áreas homólogas aparentemente normais (AHAN). Para cada área, foram obtidos valores de anisotropia fracional (FA), coeficiente de difusão aparente (ADC), MTR e tempo T2. Os encéfalos foram seccionados em fatias de 0,4mm e fotografados em alta resolução. Estas imagens foram co-registradas tridimensionalmente com as imagens de RM, utilizando técnica semi-automatizada para correlação ponto-a-ponto. Os fragmentos analisados foram corados por hematoxilina-eosina (HE), Kluverx Barrera (KB), galocianina (GALL), anti-neurofilamento (anti-NF), antiproteína básica de mielina (anti-MBP) e anti-proteína ácida fibrilar glial (anti- GFAP). RESULTADOS: Os valores de FA foram 0,40 ±0,12 nas AASSB, e 0,52±0,15 nas AHAN. Os valores de ADC foram nas AASSB de 0,129±0,04 x 10-3mm2/s, e 0,108±0,03 x10-3mm2/s nas AHAN. Os valores de MTR foram 51,59±0,88 % nas AASSB, e 52,88±4,09 % nas AHAN. Os valores de RT2 foram 91,79±1,95 % nas AASSB, e 69,94±4,54 % nas AHAN. Os valores de HE foram 162,9±20,0 nas AASSB, e 163,3±20,4 nas AHAN. Os valores de GALL foram de 181,8±4,36 nas AASSB, e 167,11±20,65 nas AHAN. Os valores de KB foram de 168,9±19,08 nas AASSB, e 182.82±20,65 nas AHAN. Os valores de NF médios mensurados foram de 131,6±12,23 nas AASSB, e 128,03±4,74 nas AHAN. Os valores de MBP médios mensurados foram de 153,9 ±13,67 nas AASSB, e 153,18±12,69 nas AHAN. Os valores de GFAP médios mensurados foram de 94.61±7,85 nas AASSB, e 81,23±6,29 nas AHAN. Os testes não paramétricos de correlação (Spearman) entre variáveis de imagens de RM e histologia apresentaram correlação apenas entre FA e GFAP (r=-0,59; p < 0,005). DISCUSSÃO E CONCLUSÕES: De acordo com os resultados obtidos, podemos inferir que a presença de gliose é um processo patológico que pode ser detectado utilizando os parâmetros de FA nas imagens de DTI. Os resultados apresentados demonstram que imagens de RM adquiridas post-mortem podem servir para compreender melhor as alterações estruturais do tecido cerebral
BACKGROUND: Diffusion tensor imaging (DTI) is part of magnetic resonance imaging (MRI) acquisition methods available in clinical exams. However, there are not enough scientific basis to infer the histological substract of DTI parameters. White matter hyperintensities (WMH) are frequent findings in clinical MRI routine. In the last years, scientific evidences show that these injuries are not just age-related benign changes, but they could be associated to pathological processes. In this study we analyzed post-mortem MRI DTI data, specifically investigating WMH, their histological and immunohistochemical correlates. OBJECTIVES : At present study, we aimed to analyze quantifiable DTI parameters - Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) - relaxometry (RT2) and magnetization transfer ratio (MTR) in WMH compared and normal appearing white matter (NAWM) from images obtained postmortem and in situ, and assess their histological substracts at WMH and NAWM using a point-topoint correlation platform. METHODS : We analyzed 20 regions of interest (ROI) encompassing WMH and NAWM selected from four subjects using in situ post-mortem MRI data acquired in 3.0T MR system. The subjects were scanned with a post-mortem interval of approximately 12h54m (±2h36m). The MRI analysis included 3D T1, FLAIR; multi-echo T2, DTI, and proton density to calculate the rate of magnetization transfer (magnetization transfer ratio - MTR). In each ROI we obtained measures of FA, ADC, RT2 and MTR. Brain specimens were posteriorly fixed in celloidin, sectioned into 0.4mm slices and photographed in high resolution. These images were co-registered with three-dimensional MR images using semi-automated technique for correlation using a point-to-point method established in our group. WMH and NAWM ROIs from MRI were submitted to quantitative histological analysis based on optical density color-deconvolution technique. Histological section were stained in hematoxylin-eosin (HE) , Kluver-Barrera (KB) , galloccyanin (GALL), anti-neurofilament (anti-NF) , anti-basic myelin protein (anti-MBP) and anti-glial fibrillary acidic protein (anti-GFAP). RESULTS: The mean FA values were 0.40±0.12 in WMH, and 0.52±0.15 in NAWM. ADC in WMH was 0.1290±0.04, x10-3mm2/s and 0.1081± 0.03 x10-3mm2/s in NAWM. MTR was 51.59± 0.88% in WMH, and 52.88±4.09% in NAWM. RT2 was 91.79±1.95% in WMH, and 69.94±4.54% in NAWM. FA, ADC and RT2 values were different between WMH and NAWM in a non-parametric analysis. On the quantitative histological analysis, the HE was 162.9±20.0 in WMH , and 163.3±20.4% in NAWM. GALL values at WMH was 181.8±4.36 and 167.11±20.65 at NAWM. KB was 168.9±19.08 in WMH, and 182.82±20.65 at NAWM. NF mean were 131.6 ±12.23 in WMH, and 128.03 ±14.74 at NAWM. MBP was 153.9±13.67 at WMH, and 153.18±12.69 at NAWM. Only GFAP values were different between WMH and NAWM. Mean GFAP was 94.61±7.85 in WMH, and 81.23±6.29 at NAWM. Non-parametric test (Spearman) between MR images and histology, showed correlation only for FA vs GFAP (r=-0.594, p < 0.005). DISCUSSION AND CONCLUSIONS: DTI FA and ADC parameters (and RT2 values) showed different patterns in WMH compared to NAWM, indicating that MR images acquired post-mortem may serve to understand the structural changes of the brain tissue. The presence of gliosis is a pathological process seems to be related to FA value from DTI
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Ferraro, Filippo Jacopo. « Magnetic anisotropies and exchange bias in ultrathin cobalt layers for the tunnel anisotropic magnetoresistance ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY086/document.

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Dans le cadre de l’étude des phénomènes magnétiques et de la spintronique qui sont présents aux échelles nanoscopiques nous avons étudié différents aspects des structures asymétriques de Pt/Co/AlOx. L’un des objectifs de cette thèse est le contrôle de l’oxydation et des propriétés magnétiques de ces multicouches. Nous avons combiné les mesures de structures (réflexion de Rayon-X), transports (Effet Hall anormal), et magnétiques (VSM-SQUID) afin de déterminer les rôles des effets magnétiques et d’interfaces. Un objectif était d’analyser le rôle de quelques monocouches (MCs) de CoO (qui peut se former lors de la sur oxydation de l’Al) sur les propriétés de la multicouche. Nous avons utilisé une technique de déposition avec un gradient d’épaisseur pour contrôler l’oxydation à l’échelle nanométrique. Nous avons établis que quelques monocouches (MCs) de CoO a un impact sur l’anisotropie de a multicouche. Pour approfondir l’effet de la couche de CoO, nous avons construit des bicouches ultrafines de Co(0.6nm)/CoO(0.6nm). Nous avons effectué des mesures refroidi sur champ sur ce système et trouvé un fort effet de couplage d'échange. Ces résultats indiquent que la couche CoO garde une forte anisotropie même en dans la limite des monocouches et permet de réfuter certains modèles sur l’effet d’échange bias et indique que les couches, couramment négligé, de CoO doivent être prises en considération dans le bilan énergétiques du système. Nous avons construits un appareil de mesure perpendiculaire de la magnétorésistance tunnel anisotrope (TAMR) à partir de la structure Pt/Co/AlOx. La TAMR est un effet de spintronique relativement récent dans lequel la rotation d’aimantation dans une électrode magnétique (combiné avec un couplage spin-orbite) peut entrainer un changement de la probabilité de l’effet tunnel, ce qui se manifeste comme un effet de magnétorésistance. Nous avons démontré qu’un contrôle précis de l’état d’oxydation est essentiel pour l’effet TAMR. La forte anisotropie magnétique induite nous permet d’atteindre des valeurs de TAMR plus grande comparée à celle des structures Pt/Co/AlOx
In the context of studying magnetic and spintronics phenomena occurring at the nanoscale, we investigated several aspects of Pt/Co/AlOx asymmetric structures. One of the objectives of this thesis was the control of the oxidation and the tailoring of the magnetic properties of these multilayers. We combined structural (X-Ray Reflectivity), transport (Anomalous Hall Effect) and magnetic measurements (VSM-SQUID), to study the interplay of magnetic and interfacial effects. One objective was to analyze the role that few monolayers (MLs) of CoO (which can form when overoxidizing the Al layer), could have on the properties of the stack. We used a wedge deposition techniques to control the oxidation on a subnanometer scale. We established that few MLs of CoO largely affect the total anisotropy of the stack. To further investigate the impact of the CoO, we engineered ultrathin Co(0.6nm)/CoO(0.6nm) bilayers. We performed field cooled measurements on this system and we found a large exchange bias anisotropy. These results indicate that the CoO keeps a large anisotropy even in the ML regime, help to rule out some of the models proposed to explain the exchange bias effect and imply that the usually neglected CoO presence must be considered in the energy balance of the system. We build perpendicular Tunneling Anisotropic MagnetoResistance (TAMR) devices based on the Pt/Co/AlOx structure. The TAMR is a relatively new spintronics effect in which the rotation of the magnetization in a single magnetic electrode (combined with the Spin-Orbit Coupling) can cause a change of the tunnel probability, which manifests as a magnetoresistance effect. We demonstrated that a careful control of the interface oxidation is crucial for the TAMR effect. The large induced magnetic anisotropy allowed us to achieve enhanced TAMR values compared to similar Pt/Co/AlOx structures
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Martins, Alessandro. « Desenvolvimento do processo de produção e estudo estrutural e magnético de filmes finos ordenados de FePt ». Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-24022014-153235/.

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Filmes de ligas FePt com uma estrutura quimicamente ordenada Tetragonal de Face Centrada FCT (tipo L1 IND.0) e textura [001] apresentam anisotropia magnética perpendicular, alta coercividade e grande efeito Kerr polar magnetoóptico. Entretanto, filmes completamente ordenados são normalmente obtidos através de um processo de \"sputtering\" com deposições em altas temperaturas do substrato(T IND. S > OU =600 ºC) ou por pós-tratamento térmico em temperaturas maiores que 500 ºC. As pesquisas atualmente em desenvolvimento visam a obtenção dessa estrutura ordenada a temperaturas mais baixas, o que seria mais adequado para aplicações práticas dos filmes. Neste trabalho, procuramos as melhores condições para a preparação de filmes de FePt com a fase ordenada FCT(001) em reduzidas temperaturas. Investigamos a influência do método de deposição, temperatura do substrato, espessura do filme e tipo de substrato sobre o grau de ordem química e textura dos filmes de FePt e, consequentemente, sobre suas propriedades magnéticas. Os filmes finos de ligas Fe IND.xPt IND. x-1(com x = 50 at%) foram preparados por \"Sputtering Magnetron DC\", através de dois diferentes métodos de deposição: pelo usual de codeposição e pelo método de deposiçãO alternada monocamadas atômicas (DAM). Os filmes foram crescidos sobre substratos de SiO IND.2/ Si(100), Si(100) e MgO(100), com e sem uma camada \"buffer\" de Pt ( com espessuras de 50 1 766 nm), sob T IND. s variando de temperatura ambiente a 600 ºC. O \"buffer\" de Pt foi usado para permitir melhores condições para a indução de um crescimento \"epitaxial\" da ordenada fase FCT(001) nos filmes de FePt. Os resultados da caracterização estrutural e magnética realizados através das técnicas de Difração de RAios-X (XRD) e Magnetometria de Amostra Vibrante (VSM) mostram que os substratos de MgO São adequados para induzir um crescimento \"epitaxial\" de filmes de FePt ) com uma estrutura FCT e textura [001]. Entretanto, com o uso de um \"buffer\" de Pt otimizado (com predominante fase FCC(100)), pré-depositado sobre MgO, foram obtifos melhores resultados em termos de \"epitaxia\" conveniente para o ordenamento da estrutura cristalina, para os filmes de FePt preparados por ambos os métodos de deposição. Os resultados mostram também que o efeito de um crescimento \"epitaxial\" induzido varia com a espessura do filme. Em relação ao método de deposição, os resultados revelam a maior eficiência de método DAM em comparação com o métodos de codeposição para a preparação de filmes de FePt com a fase FCT(001), em temperaturas reduzidas (T IND.s < OU = 400ºC). Com o uso do método DAM, foi possível a obtenção da fase ordenanda FCT(001) em filmes de FePt crescidos diretamente sobre o MgO em T IND. s = 400ºC. Para filmes de FePt crescidos sobre Pt/MgO, a formação da fase FCT(001) foi verificada em T IND.s = 200ºC e um alto grau de ordenamento químico (S = 0,88) em T IND. s = 400ºC. Estudos de Espectroscopia de Absorção de Rios-X (XAS) também foram realizados.
FePt alloy films, with a chemically ordered face-centered-tetragonal FCT (type LI IND.0) structure and [001] texture, present perpendicular magnetic anisotropy, high coactivity and large polar magneto-optical Kerr effect. However, completely ordered films are usually obtained either by sputtering process at high substrate temperatures (T IND.s MAIOR IGUAL A 600°C) or by postanneling treatment at temperatures higher than 500°C. For technological purposes the preparation temperatures has to be as low as possible. In this work we have searched the more adequate conditions to preparation of FePt films with ordered FCT(001) phase at reduced temperatures. We have investigated the influence of deposition methods, substrate temperature, thickness of film, and type of substrate on the degree of the chemical ordering and preferred texture of FePt films and, consequently, on their magnetic properties. The Fe IND.xPt IND.1-x alloy thin films (with x SEMELHANTE A 50 at%) were prepared by DC Magnetron Sputtering, via two different deposition methods: a conventional code position method and an alternate monatomic layer (DAM) deposition method. The films were grown on SiO IND.2/Si (100), Si (100) and MgO (100) substrates, with and without a Pt buffer layer (thickness ranging from 50 to 76 nm), at T IND.s varying from room temperature to 600°C. The Pt buffer layer was used for obtaining better conditions to the induction of an epitaxial grown of FePt films with the ordered FCT(001) phase. The results of structural and magnetic characterization performed by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) show that the MgO substrates are adequate to induce an epitaxial growth of FePt films with a FCT structure and [001] texture. However, with the use of an optimized Pt FCC(100) buffer layer pre-deposited on MgO, the best conditions to an epitaxial induced growth were obtained, by both deposition methods. The results show also that the quality of the epitaxial induced growth depends on the thickness of the film. In relation to the deposition method in comparison to the code position method for preparation of FePt FCT(001) films, at reduced temperatures (T IND.s MENOR IGUAL A 400°C). With the use of the DAM method it was possible to obtain the ordered FCT(001) phase in the FePt film grown directly on MgO, at T IND.s = 400°C. For FePt film grown on Pt/MgO, the formation of the FCT(001) phase was verified at T IND.s = 200°C, and high degree of chemical order (S=0,88) was obtained at T IND.s = 400°C. X-ray Absorption Spectroscopy (XAS) studies also were done.
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Costa, Marcio. « First-principles Studies of Local Structure Effects in Magnetic Materials ». Doctoral thesis, Uppsala universitet, Materialteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179223.

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This thesis focus on the magnetic behavior, from single atoms to bulk materials. The materials considered in this thesis have been studied by computational methods based on ab initio theory, density functional theory (DFT), including treatment of the spin-orbit coupling, non-collinear magnetism, and methods capable of treating discorded systems. Furthermore strongly correlated materials have been investigated using the dynamical mean field theory (DMFT). The uniaxial magnetic anisotropy energy (MAE) of the Fe2P was investigated using the full-potential linear muffin tin orbital (FP-LMTO) method. Based on a band structure analysis, the microscopical origin of the large magnetic anisotropy found for this system is explained. It is also shown that by straining the crystal structure, the MAE can be enhanced further. This opens up for the possibility of obtaining a room temperature permanent magnet based on the Fe2P. The spectral properties of Fe impurities in a Cs host have been investigated, for both surface and bulk systems, by means of combination of density-functional theory in the local density approximation and the dynamical mean-field theory (LDA+DMFT), using two different impurity solvers, the Hubbard I approximation (HIA) and the Exact Diagonalization (ED) method were used. It is shown that noticeable differences can be seen in the unoccupied part of the spectrum for different positions of Fe atoms inside the host. The calculations show good agreement with the experimental photoemission spectra. The stability of the 12-fold metal-phosphorous coordination, existing in the meteorite mineral melliniite has been investigated trough total energy calculations using the coherent potential approximation (CPA) combined with an analysis of the chemical bonds, performed by balanced crystal overlap population (BCOOP). It was shown that its uniquely high metal–phosphorous coordination is due to a balance between covalent Fe–P binding, configurational entropy and a weaker nickel–phosphorus binding. Supported clusters have drawn a lot of attention as possible building blocks for future data storage applications. This topic was investigated using a real space noncollinear formalism where the exchange interactions between Co atoms were shown to be tuned by varying the substrate surface composition. Furthermore the spin dynamics of small Co clusters an a Cu(111) surface have been investigated and a new kind of dynamics, where magnetization switching can be accelerated by decreasing the switching field, has been found. A method for calculating the electronic structure for both ordered and disordered alloys, the augmented space recursion (ASR) method, have been extended to treat non-collinear magnetic order. The method has been used to investigate the energy stability of non-collinear arrangements of MnPt and Mn3Rh alloys.
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Ouahioune, Nedjma. « MOKE set-upto measure magnetic anisotropy : MOKE set-upto measure magnetic anisotropy ». Thesis, Uppsala universitet, Materialfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414388.

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Wack, Michael Richard. « Anisotropy of magnetic remanence ». Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-145717.

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Eisenbach, Markus. « Magnetic anisotropy in nanostructures ». Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364862.

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Edström, Alexander. « Theoretical and Computational Studies on the Physics of Applied Magnetism : Magnetocrystalline Anisotropy of Transition Metal Magnets and Magnetic Effects in Elastic Electron Scattering ». Doctoral thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304666.

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In this thesis, two selected topics in magnetism are studied using theoretical modelling and computational methods. The first of these is the magnetocrystalline anisotropy energy (MAE) of transition metal based magnets. In particular, ways of finding 3d transition metal based materials with large MAE are considered. This is motivated by the need for new permanent magnet materials, not containing rare-earth elements, but is also of interest for other technological applications, where the MAE is a key quantity. The mechanisms of the MAE in the relevant materials are reviewed and approaches to increasing this quantity are discussed. Computational methods, largely based on density functional theory (DFT), are applied to guide the search for relevant materials. The computational work suggests that the MAE of Fe1-xCox alloys can be significantly enhanced by introducing a tetragonality with interstitial B or C impurities. This is also experimentally corroborated. Alloying is considered as a method of tuning the electronic structure around the Fermi energy and thus also the MAE, for example in the tetragonal compound (Fe1-xCox)2B. Additionally, it is shown that small amounts (2.5-5 at.%) of various 5d dopants on the Fe/Co-site can enhance the MAE of this material with as much as 70%. The magnetic properties of several technologically interesting, chemically ordered, L10 structured binary compounds, tetragonal Fe5Si1-xPxB2 and Hexagonal Laves phase Fe2Ta1-xWx are also investigated. The second topic studied is that of magnetic effects on the elastic scattering of fast electrons, in the context of transmission electron microscopy (TEM). A multislice solution is implemented for a paraxial version of the Pauli equation. Simulations require the magnetic fields in the sample as input. A realistic description of magnetism in a solid, for this purpose, is derived in a scheme starting from a DFT calculation of the spin density or density matrix. Calculations are performed for electron vortex beams passing through magnetic solids and a magnetic signal, defined as a difference in intensity for opposite orbital angular momentum beams, integrated over a disk in the diffraction plane, is observed. For nanometer sized electron vortex beams carrying orbital angular momentum of a few tens of ħ, a relative magnetic signal of order 10-3 is found. This is considered realistic to be observed in experiments. In addition to electron vortex beams, spin polarised and phase aberrated electron beams are considered and also for these a magnetic signal, albeit weaker than that of the vortex beams, can be obtained.

Felaktigt ISBN i den tryckta versionen: 9789155497149

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Livres sur le sujet "Magnetic anisotrophy"

1

Porter, Eithne Mary. Anisotrophy of magnetic susceptibility in the Criffel-Dalbeattie pluton, Scotland : Implications for emplacement mechanism. Birmingham : University of Birmingham, 2002.

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Tarling, D. H. The magnetic anisotropy of rocks. London : Chapman & Hall, 1993.

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F, Martín-Hernández, et Geological Society of London, dir. Magnetic fabric : Methods and applications. London : Geological Society, 2004.

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Hussain, T. Magnetic anisotropy studies of TbFe thin films. Salford : University of Salford, 1990.

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5

Greer, Allan J., et William J. Kossler. Low Magnetic Fields in Anisotropic Superconductors. Berlin, Heidelberg : Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-540-49214-6.

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Greer, Allan J. Low magnetic fields in anisotropic superconductors. Heidelberg, Germany : Springer, 1995.

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Satter, Md Abdus. A theory for dilute magnetic alloys : The origin of magnetic anisotropy. [s.l.] : typescript, 1989.

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Gupta, R. R., dir. Diamagnetic Susceptibility and Magnetic Anisotropy of Organic Compounds. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-44736-8.

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Fujita, Akira. A study on magnetic anisotropy induced in the HDDR process. Birmingham : University of Birmingham, 1999.

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Weinberger, P. Magnetic anisotropies in nanostructured matter. Boca Raton : Taylor & Francis, 2009.

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Chapitres de livres sur le sujet "Magnetic anisotrophy"

1

Buschow, K. H. J., et F. R. de Boer. « Magnetic Anisotropy ». Dans Physics of Magnetism and Magnetic Materials, 97–103. Boston, MA : Springer US, 2003. http://dx.doi.org/10.1007/0-306-48408-0_11.

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Tax, Chantal M. W., Elena Kleban, Muhamed Baraković, Maxime Chamberland et Derek K. Jones. « Magnetic Resonance Imaging of $$T_2$$- and Diffusion Anisotropy Using a Tiltable Receive Coil ». Dans Mathematics and Visualization, 247–62. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-56215-1_12.

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AbstractThe anisotropic microstructure of white matter is reflected in various MRI contrasts. Transverse relaxation rates can be probed as a function of fibre-orientation with respect to the main magnetic field, while diffusion properties are probed as a function of fibre-orientation with respect to an encoding gradient. While the latter is easy to obtain by varying the orientation of the gradient, as the magnetic field is fixed, obtaining the former requires re-orienting the head. In this work we deployed a tiltable RF-coil to study $$T_2$$ T 2 - and diffusional anisotropy of the brain white matter simultaneously in diffusion-$$T_2$$ T 2 correlation experiments.
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Skomski, Ralph, Priyanka Manchanda et Arti Kashyap. « Anisotropy and Crystal Field ». Dans Handbook of Magnetism and Magnetic Materials, 1–83. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63101-7_3-1.

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Skomski, Ralph, Priyanka Manchanda et Arti Kashyap. « Anisotropy and Crystal Field ». Dans Handbook of Magnetism and Magnetic Materials, 103–85. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63210-6_3.

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Sagnotti, Leonardo. « Magnetic Anisotropy ». Dans Encyclopedia of Solid Earth Geophysics, 1–13. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-10475-7_113-1.

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Jin, Hanmin, et Terunobu Miyazaki. « Magnetic Anisotropy ». Dans The Physics of Ferromagnetism, 205–43. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25583-0_5.

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Jansen, H. J. F. « Magnetic Anisotropy ». Dans NATO ASI Series, 349–65. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-2590-9_40.

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Sagnotti, Leonardo. « Magnetic Anisotropy ». Dans Encyclopedia of Solid Earth Geophysics, 717–29. Dordrecht : Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-8702-7_113.

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Sagnotti, Leonardo. « Magnetic Anisotropy ». Dans Encyclopedia of Solid Earth Geophysics, 923–35. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-58631-7_113.

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Dionne, Gerald F. « Anisotropy and Magnetoelastic Properties ». Dans Magnetic Oxides, 201–71. Boston, MA : Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-0054-8_5.

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Actes de conférences sur le sujet "Magnetic anisotrophy"

1

Coquaz, C., D. Challeton, Y. Souche et J. L. Porteseil. « Domains in small niFe shapes : anisotrophy versus magnetic poles ». Dans International Conference on Magnetics. IEEE, 1990. http://dx.doi.org/10.1109/intmag.1990.734947.

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Zuxiong Xu, Ruzhang Ma, Guochao Tu et Shuming Pan. « The influence of minor crystallization on the magnetic anisotrophy of iron-based amorphous alloy ». Dans International Magnetics Conference. IEEE, 1989. http://dx.doi.org/10.1109/intmag.1989.689974.

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Curtin, Paul R., Steve Constantinides et Patricia Iglesias Victoria. « Fracture Toughness of Samarium Cobalt Magnets ». Dans ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53435.

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Samarium Cobalt (SmCo) magnets have been the magnet of choice for a variety of industries for many years due to their favorable magnetic properties. Their high coercivity, combined with a low temperature coefficient, make them the ideal permanent magnet for demanding high temperature applications. One of the biggest concerns with rare earth magnets is their brittleness. Samarium Cobalt magnets in particular are prone to fracturing during machining and assembly. In manufacturing, great care must be taken to avoid chipping or fracturing these magnets due to their brittle nature. There are two main grades of Samarium Cobalt magnets, 1:5 and 2:17. These ratios define the nominal ratio of rare earth to transition metal content. In this paper, an investigation is performed on the fracture toughness of permanent magnets based on the Samarium Cobalt 2:17 composition. Various techniques are used to characterize the microstructure of the material, and quantify the material properties. Optical microscopy is used to characterize the grain structure of the material and quantify the porosity of the material after sintering. By comparing the average grain size and fracture toughness of several samples, grain size was shown to not affect fracture toughness in standard material. Latent cracks in defective material showed no preference to follow grain boundaries, oxides inclusions or voids. River marks in fracture surfaces are seen through scanning electron microscopy, confirming the transgranular cracking pattern seen by Li et al [1]This suggests that the toughness of the material is an inherent property of the main phase, not of grain boundaries or contaminants. Samarium Cobalt magnets exhibit both mechanical and magnetic anisotropy due to the alignment of their crystal structure in the manufacturing process. Using Palmqvist indentation crack techniques, the magnetic orientation of the grains was seen to greatly influence the direction of crack propagation from the tip of the indenter. Measurements of fracture toughness using this technique produce highly scattered data due to this anisotropic nature of the material. Specimens loaded with the indenter axis parallel to the direction of orientation show normal Palmqvist cracks, while specimens loaded perpendicular to the direction of magnetization exhibit crack propagation initiating from the faces of the indenter. To better quantify the material’s brittleness, fracture testing is performed on specially prepared samples to obtain an absolute measure of fracture toughness (K1c). Results show that SmCo is measurably weaker than other magnetic materials such as neodymium iron boron magnets[2]. Furthermore, neither relative concentration of Samarium nor source of raw material show notable effect on the fracture toughness of the material.
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RÜDIGER, A. « Investigations into the processing and texture of Pr-substituted NdFeB magnets produced by extrusion ». Dans Material Forming. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902479-55.

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Abstract. Crystallographically and magnetically textured but dimensionally limited NdFeB permanent magnets produced by hot deforming processes such as die-upsetting and back-extrusion have been extensively researched in the past [1]. In order to investigate the possibility of producing longer magnets which can subsequently be cut to the required length, the extrusion of permanent magnets was investigated as a further hot deformation process. For this purpose, the process control with regard to the tools used as well as the process parameters were modified from the common forming processes for extrusion. Therefore, a praseodymium-substituted NdFeB powder was encapsulated in steel and extruded by varying the extrusion ratio (9.9:1 & 13.9), the billet insert temperature (800°C & 850°C) and the extrusion speed (0.6 - 10.5 mm/s). In addition, the glass lubrication system was changed during the experiments. Since the resulting magnetic properties for hot deformation depend on the produced anisotropy, texture analyses were also carried out in the first step by means of X-ray diffraction on the cross-sections of the produced strands. For the parameter variation, strands could be realized with the applied concept. However, cracks were found in the magnetic material for all tests. Based on the texture analyses, anisotropy could be generated in the magnet material for all strands.
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Barker, Alex J., Brant Cage, Stephen Russek, Ruchira Garg, Robin Shandas et Conrad R. Stoldt. « Tailored Nanoscale Contrast Agents for Magnetic Resonance Imaging ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81503.

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Two potential molecular imaging vectors are investigated for material properties and magnetic resonance imaging (MRI) contrast improvement. Monodisperse magnetite (Fe3O4) nanocrystals ranging in size from 7 to 22 nm are solvothermally synthesized by thermolysis of Fe(III) acetylacetonate (Fe(AcAc)3) both with and without the use of heptanoic acid (HA) as a capping ligand. For the resulting Fe3O4 nanocrystals, X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and superconducting quantum interference device magnetometry (SQUID) is used to identify the average particle size, monodispersity, crystal symmetry, and magnetic properties of the ensembles as a function of time. The characterization study indicates that the HA synthesis route at 3 hours produced nanoparticles with the greatest magnetic anisotropy (15.8 × 104 J/m3). The feasibility of Fe8 single molecule magnets (SMMs) as a potential MRI contrast agent is also examined. SQUID magnetization measurements are used to determine anisotropy and saturation of the potential agents. The effectiveness of the Fe3O4 nanocrystals and Fe8 as potential MRI molecular probes is evaluated by MRI contrast improvement using 1.5 mL phantoms dispersed in de-ionized water. Results indicate that the magnetically optimized Fe3O4 nanocrystals and Fe8 SMMs hold promise for use as contrast agents based on the reported MRI images and solution phase T1/T2 shortening.
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Bram, Martin, Fernando Maccari, Monica Keszler et Tarini Prasad Mishra. « Flash Spark Plasma Sintering Of Nd-Fe-B Magnets With Tailored Anisotropic Magnetic Properties ». Dans Euro Powder Metallurgy 2023 Congress & Exhibition. EPMA, 2023. http://dx.doi.org/10.59499/ep235762561.

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Flash spark plasma sintering (Flash SPS) is an attractive alternative method for the processing of Nd-Fe-B magnets with anisotropic magnetic properties. Therefore, a load is applied on a pre-compacted sample. Then, a well-defined power pulse is applied followed by deformation and densification of the sample in seconds. Compared to established processing of anisotropic magnets via hot pressing with subsequent die-upsetting, Flash SPS introduces the possibility of electroplasticity as an additional deformation mechanism. This mechanism has the potential to improve the magnetic properties through the fine-tuning of the microstructure. Our results reveal that suitable pre-heating of the sample before applying the power pulse plays a crucial role for tailoring grain size and grain aspect ratio, both being the key for well-pronounced anisotropic magnetic properties. For better understanding of the relationship between Flash SPS parameters, microstructure and resulting magnetic properties, a systematic parameter study has been done in the present work.
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Namani, Ravi, Matthew Wood, Shelly E. Sakiyama-Elbert et Philip V. Bayly. « Anisotropic Mechanical Properties of Soft Tissues by Magnetic Resonance Elastography ». Dans ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206290.

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Structure-function relationships incorporate anisotropy of soft tissues, to account for their direction-dependent loading response [1]. Empirical measures: fiber alignment and distribution have been used to describe soft tissue response due to cell-matrix interactions and applied loads [2, 3]. To complement these measures, noninvasive estimation of anisotropic mechanical properties is essential. Magnetic resonance elastography (MRE) is a noninvasive technique to obtain elastic properties form propagating shear waves [4]. Wave propagation patterns in MRE were found to vary with direction of tissue excitation and fiber orientation [5]. Accurate estimates of anisotropic elastic properties of soft tissues have yet to be obtained by MRE.
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Victoria, Patricia Iglesias, Weimin Yin, Surendra K. Gupta et Steve Constantinides. « Microstructural Characterization of Sm-Co Magnets ». Dans ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37106.

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Samarium cobalt permanent magnets have been widely used for their excellent intrinsic magnetic properties such as very high Curie temperature, high anisotropy fields and most importantly excellent temperature coefficients of induction and coercivity. These materials have continuing industrial interest especially for applications operating at elevated temperatures and in the presence of high demagnetizing fields, such as particle accelerators, high frequency traveling wave tubes (TWTs), servo-motors and automotive and aerospace applications. An area of opportunity for improving performance of SmCo magnets is increasing magnet toughness — resistance to fracture. Like all other sintered rare earth magnetic materials, SmCo magnets are based on intermetallic compounds which are intrinsically brittle and can crack in the course of fabrication, machine work, and installation in the application. Increased toughness would also reduce handling sensitivity of magnetized magnets. For many years, studies on SmCo magnets have been focused on their magnetic properties, but the mechanical characteristics, strengthening and toughening mechanisms have been rarely reported. Understanding the phase and structural transformations induced in the SmCo magnets during the manufacturing process offers insight into potential modifications — chemical or processing-related. In this study, microstructural characterizations of 1:5 and 2:17 Sm-Co magnets were carried out using optical and scanning electron microscopes. In scanning electron microscopy (SEM), backscattered electron imaging and energy dispersive X-ray (EDX) microanalysis were used to investigate different phases and oxides. Finally, crystal structure of the magnets was studied using an X-ray diffractometer (XRD). The study correlates the microstructure characterization with the thermal processing history of different grades of SmCo magnets.
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Tweten, Dennis J., Ruth J. Okamoto, John L. Schmidt, Joel R. Garbow et Philip V. Bayly. « Identification of Anisotropic Material Parameters in Elastic Tissue Using Magnetic Resonance Imaging of Shear Waves ». Dans ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46539.

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This paper describes the application of a material parameter identification method based on elastic shear wave propagation to simulated and experimental data from magnetic resonance elastography (MRE). In MRE, the displacements of traveling transverse and longitudinal waves in elastic, biological tissue are captured as complex 3D images. Typically, the magnitude of these waves is small, and the equations of waves in linear elastic media can be used to estimate the material properties of tissue, such as internal organs, muscle, and the brain. Of particular interest are fibrous tissues which have anisotropic properties. In this paper, an anisotropic material model with three material parameters (shear modulus, shear anisotropy, and tensile anisotropy) is the basis for parameter identification. This model relates shear wave speed, propagation direction, and polarization to the material properties. A directional filtering approach is applied to isolate the speed and polarization of shear waves propagating in multiple directions. The material properties are then estimated from the material model and isolated shear waves using weighted least squares.
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Yoo, Jin-Hyeong, James B. Restorff, Marilyn Wun-Fogle et Alison B. Flatau. « Induced Magnetic Anisotropy in Stress-Annealed Galfenol Laminated Rods ». Dans ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-636.

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The recent discovery of Iron-Gallium alloy (Galfenol) as a “large” magnetostrictive material (as high as 400 ppm) offers a particularly promising transducer material that combines largely desirable mechanical attributes with superior magnetic properties [1]. The high permeability of this material makes it easy to magnetize, however it also causes a relatively low cutoff frequency in dynamic applications, above which eddy currents form and introduce significant power losses. To reduce the eddy current losses, magnetostrictive drivers used in dynamic applications are commonly laminated. A second transducer design consideration is the introduction of an initial alignment of domains inside of the material to maximize the magnetostriction performance. It is common to achieve this by imposing an external compressive prestress to align magnetic moments perpendicular to the direction of actuation. An alternative to the application of an external prestress is to build-in a uniaxial magnetic anisotropy through stress annealing [2]. Stress annealing is a high temperature process with simultaneous application of an external load and subsequent cooling under load in which the magnetic moment alignment developed at temperature is retained upon removal from the stress annealing fixture. The external load needed to build in a useful uniaxial magnetic anisotropy in Galfenol is greater than the buckling load for Galfenol laminae sized for use in high frequency dynamic applications. In this study, prior work on stress annealing of solid rods of single and polycrystalline samples of Galfenol is successfully extended to thin laminae of Galfenol by introducing fixtures to avoid buckling of the laminae under compression during the heat treatment process. Values of the uniaxial anisotropy, cubic anisotropy, saturation magnetic induction, and saturation magnetostriction were obtained from measurements of the magnetization and magnetostriction of stress-annealed Galfenol strip as a function of compressive and tensile stress. These values were derived from fitting magnetization and magnetostriction curves to the energy expression formula [3]. Data are presented that demonstrate the magnetic uniaxial anisotropy developed by stress annealing of laminated Galfenol rods. An annealing temperature of 500 °C and a compressive stress of 200 MPa produced a uniaxial anisotropy of 11.3 kJ/m3 in this study.
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Rapports d'organisations sur le sujet "Magnetic anisotrophy"

1

Choudhury, Sarah, Ross Underhill et Thomas Krause. PR-652-203801-R04 Magnetometer Noise and Resolution. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), novembre 2021. http://dx.doi.org/10.55274/r0012196.

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Magnetometers are sensors that measure the magnitude and direction of a magnetic field. There are many types of magnetometers available, but they all rely on electromagnetic principles to measure fields. The most common types are Hall effect, anisotropic magneto-resistive (AMR) and fluxgate sensors. The goal of this study is to investigate several magnetometers to evaluate their capability to detect small changes in an ambient field. These small changes are on the order of 10 milligauss (1 �T) and are caused by the inverse-magnetostrictive effect, or Villari effect, from ferromagnetic pipes. The chosen magnetometer must have a low noise signal and a fine resolution to properly measure the field from the inverse-magnetostrictive effect. To evaluate the chosen magnetometers, multiple sets of measurements were made in a stationary magnetic field and the standard deviation of the data sets were calculated. The noise of some sensors was further investigated to verify that it was normally distributed.
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Pechan, M. J. Magnetic multilayer interface anisotropy. Office of Scientific and Technical Information (OSTI), janvier 1991. http://dx.doi.org/10.2172/5158883.

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Pechan, M. J. Magnetic multilayer interface anisotropy. Office of Scientific and Technical Information (OSTI), janvier 1992. http://dx.doi.org/10.2172/6958467.

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Pechan, M. J. Magnetic multilayer interface anisotropy. Office of Scientific and Technical Information (OSTI), janvier 1990. http://dx.doi.org/10.2172/6554380.

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Freedman, Danna, et Alison Altman. Permanent Magnets Featuring Heavy Main Group Elements for Magnetic Anisotropy. Office of Scientific and Technical Information (OSTI), novembre 2022. http://dx.doi.org/10.2172/1899082.

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Toney, Michael F. High Anisotropy CoPtCrB Magnetic Recording Media. Office of Scientific and Technical Information (OSTI), juin 2003. http://dx.doi.org/10.2172/813356.

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Ernst, R. E., et G. W. Pearce. Averaging of Anisotropy of Magnetic Susceptibility Data. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1990. http://dx.doi.org/10.4095/128071.

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8

Hellman, Frances. Sources of Anisotropy in Amorphous Magnetic Thin Film. Fort Belvoir, VA : Defense Technical Information Center, avril 1992. http://dx.doi.org/10.21236/ada252296.

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Hellman, Frances. Sources of Anisotropy in Amorphous Magnetic Thin Films. Fort Belvoir, VA : Defense Technical Information Center, novembre 1990. http://dx.doi.org/10.21236/ada230542.

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Diaz, J., N. M. Hamdan, P. Jalil, Z. Hussain, S. M. Valvidares et J. M. Alameda. Understanding the magnetic anisotropy in Fe-Si amorphous alloys. Office of Scientific and Technical Information (OSTI), août 2002. http://dx.doi.org/10.2172/820783.

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