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 P < P B , 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 .