Anomalous temperature dependence of magnetization in single-crystal Fe 65Ni 35 alloy

Abstract

Magnetization (0–10 Oe) and magnetic relaxation measurements were carried out in the temperature range between 4.2 and 300 K for three picture-frame samples of Fe 65Ni 35 alloy whose edges were parallel to 〈100〉, 〈110〉 and 〈111〉, respectively. The typical temperature T g and the magnetic field H g which correspond to the anomalous temperature in the χ- T curve and inflection field in the σ- H curve, respectively are summarized and H- T g and H g- T diagrams are obtained. A strong magnetic relaxation is observed along the H g- T line. The dependence of H g on the crystallographic direction and on the temperature are discussed by the thermal activation process of the 180° domain wall which is pinned strongly by the antiferromagnetic clusters below T g. The anomaly of magnetization of Fe 65Ni 35 alloy can be interpreted by the macroscopic picture of the coexistence of ferromagnetic and antiferromagnetic-like regions which may be caused by a statistical fluctuation of alloy composition.