Origin of anomalous increase of hyperfine field in Dy(Ni xCu 1− x) 2Si 2

Abstract

161Dy Mössbauer experiments at 3 K were performed on pseudo-ternary Dy(Ni x Cu 1− x ) 2Si 2 compounds of 0 ≤ x ≤ 0.15 in order to clarify an origin of anomalous increase of hyperfine field in the mixed compounds. The Mössbauer spectra of the mixed compounds are interpreted satisfactorily by three Zeeman subspectra. The concentration dependence of intensity ratio of three subspectra indicates that the hyperfine field depends strongly on the number of substituted Ni atoms in the nearest and next nearest transition metal sites which break the local tetragonal symmetry. The Dy atoms surrounded by the nearest neighbors containing both Cu and Ni atoms have large hyperfine fields close to the value of a pure |J z = − 15 2 〉 state. The local disturbance of crystalline electric field also brings forth the change of single-ion magnetic anisotropy. And then saturation magnetization decreases as the Ni content increases, since a part of Dy moments are arranged noncollinearly.