Transições de fase e propriedades magneticas de compostos R-T

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

In this work we studied intrinsic and extrinsic magnetic properties of rare earth-transition metals compounds. The intrinsic magnetic properties of R(Fe,M)12 intermetallic compounds was systematically investigated. Emphasis was given to the determination of magnetic phase transitions and magnetocrystalline anisotropy field. Measurements of the temperature dependence of the a.c. susceptibility was used to study magnetic phase transitions induced by temperature, like spin reorientation transitions, occurring between 4.2 K and 300 K. The singular point detection technic (SPD) associated to pulsed fields was used to measure the anisotropy field and the critical field of field induced magnetic phase transitions (FOMP) in the temperature range of 4.2 K to 300 K, using magnetic fields up to 28 T. The results obtained for YFe12-xMox compounds indicate that the transition metal has an uniaxial contribution to the anisotropy. A high uniaxial anisotropy was found only in SmFe12-xMox compounds. Spin reorientation transitions were found in the RFe12-xMox systems with R=Nd, Dy and Er. FOMP like transitions were found in the ErFe12-xMox samples. Nitrogenation experiments were performed with the RFe12-xMox samples (R = Y and Nd). The results show that the nitrogen has a strong influence not only in the rare earth anisotropy, but also change the F e anisotropy from uniaxial to planar after nitrogenation. We also investigated the magnetization reversal processes in Sm2Fe17Nx magnets produced by Zn-bond and HDDR. The temperature dependence of the coercive field was measure in the range from 4.2 K to the Curie temperature. The effects of different recombination temperatures and different Zn contend were studied. The results were analyzed based in the Kronmuller s micromagnetic model that takes into account microestructural parameters. A nucleation mechanism was proposed as a leading mechanism of magnetization reversal in this magnets

ASSUNTO(S)

terras raras compostos de metais de transição compostos intermetalicos anisotropia imas permanentes

ACESSO AO ARTIGO

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