Electronic specific heat and high field magnetization studies on the Y6(Fe1−xMnx)23 system

Magnetizations at applied fields up to 120 kOe and electronic specific heats have been determined for ternaries represented by the formula Y₆(Fe_1?xMn_x)₂₃. The Curie temperature and ordered magnetic moment of Y6Mn₂₃ and Y₆Fe₂₃ decrease sharply when these materials are formed into solid solutions, being minimal in the vicinity of the equimolal solution. To test whether the reduction is a band effect electronic specific heats were measured; they are maximal where T_c and the moment are minimal, indicating unimportance of band effects. Curie-Weiss behavior is exhibited at low fields, suggesting rather localized d-electrons. The nearest neighbor distances are such as to lead to antiferromagnetic Mn-Mn interactions. Y₆Mn₂₃ is taken to be ferrimagnetic whereas Y₆Fe₂₃ appears to be ferromagnetic. While the magnetic structure of the ternaries is yet to be fully clarified, it is clear that antiferromagnetic exchange is enhanced when either binary is formed into a ternary. It also appears that the Mn-Fe coupling is antiferromagnetic in the ternaries.