Local magnetic properties of iron-rich amorphous Fe100−xZrx alloys

Abstract We report results of 57 Fe Mossbauer measurements on the magnetically concentrated re-entrant spin-glass amorphous Fe 100− x Zr x alloys (8⪕ x ⪕12) which give convincing evidence for a microscopic origin of the low-temperature magnetization anomaly at T f T C . This is shown by an anomalous increase in the magnetic hyperfine field and in the relative intensities of the (Δm=0)-Mossbauer lines below T f upon cooling. No evidence was found for an antiferromagnetic phase. The shape of the hyperfine-field distribution at T =4.2 K in zero external field and in a field of 3 T is unchanged, indicating homogeneous behaviour of all Fe moments near saturation. Ferromagnetic order is not long-ranged, but determined by exchange-coupled magnetic clusters. The cluster moment near T C is found to decrease strongly with increasing Fe content and extrapolates to zero at x ≈96.