Crystal-field Γ₈-like State in Magnetically Ordered Phases of CeP: Its Anisotropy and Influence on Electronic Structure via High-Field Magnetotransport Measurements

Abstract

Although the crystal-field ground state in the paramagnetic phase of CeP is Γ₇, part of cerium ions take a Γ₈-like state in magnetically ordered phases and regular arrangements of the Γ₇ and Γ₈-like moments constitute magnetic structures. We have performed transverse magnetoresistance measurements up to 32 T for selected field directions and have determined phase boundaries related to the appearance of the Γ₈-like state for each field direction. The result reveals the extreme uniaxial anisotropy that the Γ₈-like moment is strongly bound to the [001] axis. We have also determined the field-orientation dependence of phase transitions connected with the rearrangement of the Γ₇ moment via ac susceptibility measurements. The analysis of the angular dependence indicates that the Γ₇ moment prefers the [001] direction only weakly probably due to the exchange field from neighboring Γ₈ moments. The resistivity exhibits a sharp decrease on the appearance of the Γ₈-like state. Besides, Hall effect measurements up to 26 T show a concomitant reduction of the magnitude of the Hall coefficient, and suggest the presence of the anomalous Hall effect in the magnetically ordered phases. These indicate that the appearance of the Γ₈-like state is accompanied by a drastic change of the electronic structure.