Possible existence of magnetic polaron in nearly ferromagnetic semiconductor -US

Ikeda, Shugo*; Sakai, Hironori   ; Tateiwa, Naoyuki   ; Matsuda, Tatsuma; Aoki, Dai*; Homma, Yoshiya*; Yamamoto, Etsuji  ; Nakamura, Akio; Shiokawa, Yoshinobu*; Ota, Yuki*; Sugiyama, Kiyohiro*; Hagiwara, Masayuki*; Kindo, Koichi*; Matsubayashi, Kazuyuki*; Hedo, Masato*; Uwatoko, Yoshiya*; Haga, Yoshinori   ; Onuki, Yoshichika

We studied the magnetic properties of a paramagnet -US with the orthorhombic crystal structure by measuring the magnetization, magnetic susceptibility, specific heat and electrical resistivity under magnetic field and pressure. The 5-crystalline electric field (CEF) scheme was determined from the experimental results The insulating resistivity is drastically changed to a metallic one under high pressure 8 GPa similar to that of the semimetallic Ising-type ferromagnet UTeS with the Curie temperature =87 K. From these experimental results, it was concluded that -US is in the vicinity of the ferromagnetic ordering at ambient pressure. The anomalous magnetization was analyzed on the basis of the ferromagnetic cluster and discussed from a viewpoint of the magnetic polaron.