On the Metamagnetic Behavior of Fe_0.864Se Single Crystals

Abstract

Magnetization measurements on Fe_0.864Se (3c type) single crystals have been carried out around the temperature of spin axis transition (T_s=150 K). Above T_s, the material behaves as a usual ferrimagnet having the easy plane (c plane). Below T_s where the c axis is the easy direction, the observed magnetization curves have some resemblance to those of metamagnets: A sudden increase of magnetization occurs at a certain value of the applied field (10³∼10⁴ Oe) depending upon the field direction and the temperature. The hysteresis loop takes a constricted form with very small remanence (<5% of the saturation value). The composition range where these anomalies are observed is extremely narrow. The process of magnetization below T_s is described as a field-induced first-order magnetic transition of the system of antiferromagnetically coupled regions. The origin of such regions is also discussed.