COMPETING EXCHANGE INTERACTIONS AND THEIR RELEVANCE FOR THE MAGNETIZATION PROCESS IN RMN(6-X)CR(X)SN(6) POWDERS (R=Y, GD, TB, DY, HO, ER)

The free-powder magnetisation of RMn(6)-xCrxSn6 compounds has been mea sured for compounds with R = Y, Gd, Tb, Dy, Ho, Er in fields up to 38 T, and interpreted in terms of a simple model, which is also outlined in this paper. From the measurements, estimates for the R-3d mean-fiel d coupling constant (n(RT)) could be derived for the cases where R = G d, Tb, Dy, Ho, Er. In turn, the n(RT) values can be related to the mic roscopic spin-coupling constant (J(RT)). In the case of YMn6Sn6 the hi gh-field measurement presents evidence for a very weak antiferromagnet ic coupling between the Mn layers. Furthermore, values for the Mn mome nts (mu(Mn)) were also derived from the magnetisation measurements. Th e estimated mu(Mn) values are of the order of 2.0 mu(B).