Suppression of -electron itinerancy in CeRuSi by a strong magnetic field

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J. L.*; Michimura, Shinji*; Inami, Toshiya; Kindo, Koichi*; Ebihara, Takao*

The valence state of Ce in a typical heavy fermion compound CeRuSi has been investigated by synchrotron X-ray absorption spectroscopy at 1.8 K in high magnetic fields of up to 40T. The valence was slightly larger than for the pure trivalent state, as expected in heavy fermion compounds, and it decreased toward the trivalent state as the magnetic field was increased. The field-induced valence reduction indicates that the itinerant character of the 4 electrons in CeRuSi was suppressed by a strong magnetic field. The suppression was gradual and showed a characteristic magnetic field dependence, which reflects the metamagnetism around 8T.