GD-155 MOSSBAUER STUDY OF GDMN2GE2

A new Gd-155 Mossbauer study of GdMn2Ge2 has been undertaken. Our Mossbauer data are in agreement with single crystal magnetization measurements which showed that the Gd moments are along the c-axis. The slight deviation of H(hf) from the c-axis (theta = 20-degrees) suggests the occurrence of anisotropic contributions to H(hf). The quadrupole interaction data allow to estimate the second order crystal field parameter B2(0) for the isostructural RMn2Ge2 series. From the negative sign of e2q(Z)Q it may be anticipated that the easy direction of magnetization of the rare earth sublattice should be parallel to the c-axis when the Stevens factor alpha-(J) is negative (e.g. in DyMn2Ge2) and in the basal plane when alpha-(J) is positive (e.g. in ErMn2Ge2). These predictions are found to be in agreement with neutron or single crystal magnetization data for several RMn2Ge2 compounds. In field Mossbauer measurements indicate that the hyperfine field is negative.