Competing exchange interactions and their relevance for the magnetisation process in RMn6-xCrxSn6 powders (R=Y, Gd, Tb, Dy, Ho, Er)

The free-powder magnetisation of RMn6-xCrxSn6 compounds has been measured 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-field coupling constant (nRT) could be derived for the cases where R=Gd, Tb, Dy, Ho, Er. In turn, the nRT values can be related to the microscopic spin-coupling constant (JRT). In the case of YMn6Sn6 the high-field measurement presents evidence for a very weak antiferromagnetic coupling between the Mn layers. Furthermore, values for the Mn moments (μMn) were also derived from the magnetisation measurements. The estimated μMn values are of the order of 2.0 μB. ((orig.))