MOSSBAUER, MAGNETIC, AND ELECTRONIC-STRUCTURE STUDIES OF YFE12-XMOX COMPOUNDS

Mossbauer spectra, magnetization measurements, and self-consistent spi n-polarized electronic structures of YFe12-xMox, where x =0.5, 1.0, 2. 0, 3.0, and 4.0, are reported. The ternary compounds YFe12-xMox have t he crystalline tetragonal ThMn12 structure. Analyses of the Mossbauer spectra show that Mo atoms occupy the 8i Fe sites of the ThMn12 struct ure, in agreement with previous observations. Room-temperature magneti c and Mossbauer measurements show that the compounds with x less than or equal to 2.0 are ferromagnetic and with x greater than or equal to 3.0 are paramagnetic. Measurements at 25 K show that all the samples a re magnetically ordered. The magnetic hyperfine field is found to decr ease with increasing Mo concentration, which is in qualitative agreeme nt with the calculated magnetic moments. The calculated magnetization decreases less rapidly with increasing x than the experimental data. I n general the data suggest that with increasing Mo concentration there is an increase of antiferromagnetic coupling among the Fe moments, wh ich leads to cluster-glass or spin-glass-like phenomena. The measured isomer shift relative to a-iron is found to decrease linearly with x.