Pressure-induced ferromagnetic quantum criticality in the low-carrier system CeP

Abstract

We have already obtained the tentative pressure (P)-temperature (T) magnetic phase diagram of the antiferromagnetic (AF) semimetal CeP with strongly localized 4f electrons by measurements of the only T-dependence of the electrical resistivity, ρ(T), up to 8 GPa. In order to get further reliability, we performed the simultaneous measurements of the T- dependent real part of the AC magnetic susceptibility, χ'AC(T), and ρ(T) at P ≲ 2.5 GPa. As a result, the temperature which give the resistive anomaly was found to be the exact transition temperature from the paramagnetic (PM) phase to the magnetically ordered state, even in P > 2.5 GPa. The detailed magnetic structures (MSs) is already clarified by the neutron diffraction (ND) experiments under high pressures up to 1.7GPa by Kohgi et al. and up to 5.6 GPa by Goncharenko et al. The careful comparison between our macroscopic P-T magnetic phase diagram and the microscopic MSs elucidated the new facts: in the high-P region, the induction of the pure ferromagnetic (FM) phase for P ≳ 4 GPa is revealed to cause a rapid decrease in the Curie temperature TC and the Ce localized magnetic moment (LM); and furthermore, the TC is observed to vanish at a critical pressure PC ≈ (5.5±0.1) GPa together with the LM. We report the convincing basis for the presence of a P-induced FM quantum critical point (FM- QCP) and the possibility of localized-delocalized transition of the Ce-4f states approximately at the FM-QCP in the semi-metallic LM system CeP with the extremely low-carrier density.