Transport Properties of EuNi2Ge2 under High Pressure

Abstract

Transverse magnetoresistance (MR) and Hall effect have been measured for EuNi2Ge2 single crystals under high pressures up to 2.0 GPa. The compound undergoes a valence transition from a nearly trivalent state to a divalent state with increasing temperature above 1.6 GPa. It was found that the transverse MR of EuNi2Ge2 is negative at low temperatures in the nearly trivalent state, although the compound is nonmagnetic. The origin of the negative MR is discussed. In the temperature dependence of the Hall resistivity ρH, large jumps associated with the valence transition were observed at the valence transition temperature. We also examined the field-induced valence transition by the MR and ρH measurements. A marked change in the Hall coefficient was observed at the valence transition field. Our analyses suggest that the ordinary Hall effect plays a dominant role in the changes in ρH at the valence transition.