SPIN-GLASS PHENOMENA IN TBFEXAL12-X

Magnetization and 57Fe Mossbauer spectroscopy measurements of TbFexAl12-x (x=3.5, 4, 4.5, 5, 5.5, 6) at temperatures 4.2 to 350 K have been performed. The Mossbauer studies yield the iron relative occupation of the three, (f), (j) and (i), inequivalent crystallographic sites in the tetragonal (I4/mmm) unit cell, their hyperfine field distributions and the magnetic ordering temperatures. These are quite similar to those previously reported for YFexAl12-x. The magnetization measurements, however, display quite different phenomena than those observed for YFexAl12-x. The contribution of the Tb sublattice to the magnetization with its associated high magnetic anisotropy and the spin glass structure in the iron sublattices lead to the wide variety of unusual phenomena observed. The more common phenomena associated with the spin glass structure, namely, differences between field cooled and zero field cooled magnetization curves, thermoremanent and isothermal remanent magnetization and their time dependences were also observed.