Analysis of magnetization behavior in magnetic semiconductor -US

磁性半導体-USの磁気的性質の分析

山本 悦嗣  ; 立岩 尚之   ; 芳賀 芳範   ; 池田 修悟*; 酒井 宏典   ; 大貫 惇睦; Fisk, Z.

Yamamoto, Etsuji; Tateiwa, Naoyuki; Haga, Yoshinori; Ikeda, Shugo*; Sakai, Hironori; Onuki, Yoshichika; Fisk, Z.

-US is a paramagnetic semiconductor. Chemical substitution of the sulfur site or application of hydrostatic pressure induces ferromagnetic ordering, indicating that -US is located near the ferromagnetic instability. Application of magnetic field leads to a huge negative magnetoresistance in -US and this behavior is discussed based on the magnetic polaron. In the present study, we study the magnetic, transport and thermal properties of -US in detail to clarify the anomalous behavior. Magnetization measurements at low temperature can roughly be explained by a ferromagnetic cluster behavior where the number of the cluster is equal to the number of carrier estimated from Hall effect measurements, consistent with the magnetic polaron model.