57Fe Mossbauer and magnetic studies of DyFe12-xTax compounds

Refinements of the X-ray diffraction patterns show that DyFe12-x Ta (x) compounds with x = 0.5-0.7 crystallise in the ThMn12-type structure and that the Ta atoms occupy the 8i sites. Spin reorientations have been detected by ac magnetic susceptibility for all compounds below room temperature. First the moments shift direction from easy axis to easy cone at T (sr1), then to easy plane at T (sr2). Both T (sr1) and T (sr2) increase with increasing Ta content up to x = 0.65 before decreasing with further increase in Ta content. Analyses of the Mossbauer spectra indicate that the individual Fe site hyperfine fields derived at 4.5 K for DyFe11.35Ta0.65 are B (hf) = 37.4 T, 32.2 T and 27.6 T for the 8i, 8j and 8f sites, respectively.