A Mössbauer effect study of the magnetic ordering in the Y6(FexMn1−x)23 solid solutions

The ternary alloys, Y₆ (Fe_xMn_1–2)₂₃, exhibit interesting magnetic behavior over a range of solid solutions of iron and manganese. The transition metal atoms occupy four crystallographically different sites. For x less than ca. 0.27, the transition metal atoms couple ferromagnetically, whereas for greater values of x they couple antiferromagnetically. By using the iron populations for each site, obtained from neutron diffraction studies, it is possible to determine the Mössbauer effect hyperfine parameter fields for each site. As x increases, the ordering temperature decreases dramatically. At 1.3K in Y₆Fe₂₃, the four hyperfine fields range from 372kOe to 250kOe, whereas in Y₆(Fe_0.52Mn_0.48)₂₃ they decrease to values between 100kOe and 10kOe. This decrease apparently results from the increasing frustration of the ferromagnetic iron-iron coupling as additional manganese, which would prefer antiferromagnetic coupling, is introduced into the alloys.