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Enhancing magnetic properties of anisotropic NdDyFeCoNbCuB powder by applying magnetic field at high temperature during hydrogen desorption

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Rare Metals 2010年第5期29卷 480-485页

作者： LUO Jianjun P. De Rango D. Fruchart MEI Jinna HU Rui LI Jinshan ZHOU Lian State Key Laboratory of Solidification Processing Northwestern Polytechnic University Xi'an 710072 China Matière Condensée Matériaux et Fonctions ( mcmf ) lnstitut Néel CNRS BP 166 38042 Grenoble Cedex 9 Francec Consortium de Recherches pour l'Emergence de Technologies Avancées ( CRETA ) CNRS BP 166 38042 Grenoble Cedex 9 France

Anisotropic powder was prepared with precursor （NdDy）-（FeCoNbCu）-B sintered magnets by hydrogen decrepitation, desorption, and subsequent annealing treatment. The hydrogen desorption was performed in magnetic fields of 0, 1, 3, and 5 T. The orientation of tetragonal phase grains of the powder was evaluated from the hysteresis loops measured by extraction magnetometer. Residual hydrogen content of the powder was evaluated by thermal-magnetic analysis. The powder with Hcj, Br, and （BH）max of 1138 kA.m^-1, 1.029 T, and 172.5 kJ.m^-3, respectively, was achieved under the condition of the magnetic field of 3 T. Magnetic properties of the powder, especially, the remanence of the powder, are enhanced upon magnetic fields, which is due to better orientation of powder particles and less residual hydrogen in the powder resulted from the magnetic field during the hydrogen desorption process.

关键词： permanent magnets hydrogen absorbing materials anisotropy magnetic measurements magnetic properties

Magnetic and specific heat studies of the frustrated Er_2Mn_2O_7 compound

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Journal of Rare Earths 2013年第1期31卷 54-59页

作者： N.Ben Amor M.Bejar E.Dhahri M.A.Valente P.Lachkar E.K.Hlil Laboratory of Applied Physics Faculty of Sciences of SfaxBP 1171University of Sfax I3N and Physics Department University of Aveiro mcmf Néel InstitutCNRS25 avenue des MartyrsBuilding FBP 16638042 Grenoble cedex 9France MCBT Institut NéelCNRS25 avenue des MartyrsBuilding EBP 16638042 Grenoble cedex 9France

A new ErzMn207 compound was synthesized by the ceramic method and its crystal structure was characterized LJsing powder X-ray diffraction （XRD） and observed by scanning electron microscopy （SEM）. The magnetic properties were investigated using a BS2 magnetometer and the heat capacity was studied using a quantum design （PPMS）. The structural study revealed that this compound was monophasic and crystallized in the monoclinic system with the P2/M space group. Magnetization measurements were carried out in the temperature range of 1.8-200 K under an applied magnetic field of 0.05 T. A crossover from a room temperature para- magnetic phase to an antiferromagnetic one at low temperature was detected from the magnetic study. The magnetic susceptibility, in the paramagnetic region above 40 K, was found to present a simple Curie-Weiss type behavior. From the specific heat （G,） measurements in magnetic fields up to 5 T, we noted the presence of a wide peak characteristic of a second order magneto-structural transition.

关键词： magnetic frustration magnetic phase transition specific heat rare earths

Electronic and magnetic structures of V-doped zinc blende Zn_(1-x)V_xN_yO_(1-y) and Zn_(1-x)V_xP_yO_(1-y)

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Chinese Physics B 2011年第8期20卷 419-424页

作者： N.Mamouni M.Belaiche A.Benyoussef A.El Kenz H.Ez-Zahraouy M.Loulidi E.H.Saidi E.K.Hlil Laboratoire de Magntisme et de Physique des Hautes Energies Dpartement de Physique Associ au CNRSTURACB.P.1014Facult des SciencesRabatMorocco Laboratoire de Magntisme Matriaux MagntiquesMicro-ondes et CramiqueENSRabatMorocco INANOTECH Institute of Nanomaterials and NanotechnologyMAScIRRabatMorocco Laboratoire de Physique des Hautes Energies Dpartement de Physique B.P.1014Facult des SciencesRabatMorocco Institut Nel MCMF-UJFC.N.R.SB.P.16638042 Grenoble CedexFrance

Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker （KKR） method combined with the coherent potential approximation （CPA）. Calculations for the substitution of O by N or P are performed and the magnetic moment is found to be sensitive to the N or P content. Furthermore, the system exhibits a half-metallic band structure accompanied by the broadening of vanadium bands. The mechanism responsible for ferromagnetism is also discussed and the stability of the ferromagnetic state compared with that of the paramagnetic state is systematically investigated by calculating the total energy difference between them by using supercell method.

关键词： ab initio calculations density of states magnetic moment doping diluted magneticsemiconductors