Münster 1999 – wissenschaftliches Programm
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AM: Magnetismus
AM 2: Dauer- und weichmagnetische Werkstoffe
AM 2.5: Vortrag
Montag, 22. März 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 CHENG1,2 — 1Max-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.