MAGNETISM AND HYPERFINE INTERACTIONS OF FE-57, EU-151, GD-155, DY-161, ER-166 AND YB-170 IN RM4AL8 COMPOUNDS (R = RARE-EARTH OR Y, M = CR, MN, FE, CU)

Mössbauer and magnetic susceptibility studies of sixty tetragonal RM4Al8 compounds (R = 4f, M = 3d element), show a wide variety of magnetic phenomena in the behaviour of 3d transition elements. The rare earths order antiferromagnetically at temperatures below 10-30 K in all compounds. The 3d elements, however, all behave differently. Fe in RFe4Al8 has a localized moment (effective moment of 4.4 μB) and orders independently of the rare earth sublattice. Mn in RMn4Al8 has also a localized moment (∼1 μB) but orders only when the rare earths order. Cr in RCr4Al8 has no moment of its own, but it has an induced moment (.1 μB) by its magnetic rare earth neighbours. Cu in RCu4Al8 is nonmagnetic. The Mössbauer studies of 151Eu, 155Gd, 161Dy, 166Er, 170Yb and a 57Fe probe yield all hyperfine interaction parameters including the orientation of the hyperfine field relative to the crystallographic c-axis. In addition, the studies yield the Ce, Eu and Yb valencies in the various compounds. Eu in EuFe4Al8 and in EuMn4Al8 and Yb in YbCr4Al8 are in a mixed valent state. © 1979.