Low dimensional intermediate valence fluctuation in single crystalline YbB4

Abstract

Temperature-dependent magnetization M(T), resistivity rho(T), and specific heat C-p(T) were measured for single crystalline YbB4. M(T) showed a large anisotropy, that is M-parallel to(T)>M-perpendicular to(T), for fields parallel and perpendicular, respectively, to the c axis. While M-parallel to(T) followed Curie-Weiss behavior with slight crystalline electric field splittings, M-perpendicular to(T) showed a typical temperature dependence of intermediate valence (IV) fluctuation, which implies that YbB4 is a rare compound with two-dimensional IV fluctuation. rho(T) followed rho(0)+AT(2) below T-coh approximate to 5 K, indicating a low-temperature Fermi liquid state of YbB4. In addition, anomalies were also found at approximate to T-coh in M(T), rho(T), and C-p(T).