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Münster 1999 – scientific programme

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AM: Magnetismus

AM 2: Dauer- und weichmagnetische Werkstoffe

AM 2.5: Talk

Monday, March 22, 1999, 10:45–11:00, F4

The structure and magnetic properties of R2Co17−xGax (x=0-8) compounds with R = Y, Gd and Tb — •BING LIANG1,2, BAO-GEN SHEN2, SHAO-YING ZHANG2, and ZHAO-HUA CHENG1,21Max-Planck-Institut für Metallforschung, Heisenbergstr. 1, 70569 Stuttgart — 2 State  Key  Laboratory  of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, P.R. China

The R2Co17−xGax (R=Y, Gd and Tb) compounds were prepared directly by arc-melting with a subsequent annealing. The structural and magnetic characteristics of these compounds have been investigated by means of XRD and magnetic measurements. The XRD patterns show that all samples are single phase with the 2:17-type except those samples with x=7 and 8 which contain small amounts of hcp Co and rare-earth-rich phase as impurity phases. The Ga substitution for Co in these compounds leads to a monotonic increase in unit cell volume and an approximately linear decrease in saturation magnetization. The Curie temperature is found to decrease rapidly with increasing Ga concentration. Compensation points are observed in the  temperature dependence of the magnetization for Gd2Co17−xGax and  Tb2Co17−xGax samples with x=4, 5 and 6 . The intersublattice-molecular-field  coefficients, nRT, have been deduced on the basis of magnetization curves at corresponding  compensation temperatures. The exchange-coupling constants JRT and JTT  have been calculated by analysing both the field dependence and the temperature  dependence of the magnetization. It has been found that the substitution of Ga  for Co in these compounds reduces the Co-Co exchange interaction, while it has  little influence on the R-Co exchange interaction. It is noteworthy that the Ga substitution  has changed the room-temperature easy magnetization direction(EMD) for Gd2Co17−xGax,  while the room-temperature EMD for Y2Co17−xGax and Tb2Co17−xGax  remain unchanged with the Ga substitution.
The work was support by the National Natural Sciences Foundation of China.

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