Pressure Effects on Crystal Electric Field Excitations in Ultra-Low-Carrier Kondo-Lattice Systems CeP and CeAs

Abstract

Pressure effects on crystal electric field (CEF) excitations in ultra-low carrier systems CeP and CeAs have been studied up to 2.8, GPa. There are two critical pressures P_c and P_B: 0.25, GPa and 1.1, GPa for CeP, while 1.3, GPa and 2.5, GPa for CeAs, respectively. CEF excitations are well-defined for PB, and there is no anomaly at the onset pressure of the ferromagnetic order, P_c. In contrast, striking anomalies have been observed around P_B. For CeP, the CEF excitation decreases to 12, meV and a new CEF excitation appears at 9, meV near P_B, then it gradually replaces the first one above P_B. For CeAs, a CEF excitation exhibits strong softening as well as broadening near P_B. Finally, the CEF spectra exhibit strong broadening around 40, K in the low tempe rature phase near and above P_B.