The influence of crystal electric field on thermal properties of non-stoichiometric ErB50 boride at low temperatures

Abstract The temperature dependences of heat capacity, C p (T) , and lattice parameters, a(T) , b(T) , c(T) , of ErB 50 in the temperature range of 2–300 K were experimentally studied. Two features in C p (T) were observed: a maximum at T m1  = 3.12 K, that is associated with a magnetic ordering (transition to an antiferromagnetic state), and a broad anomaly at about T m2  = 27 K that is due to the effects of the crystal electric field (CEF) on the boride heat capacity. Based on these data a scheme of splitting of Er 3+ ions f-levels by the crystal field was suggested. Comparison of the temperature dependence of unit cell volume V(T) for ErB 50 with the literature data for LuB 50 revealed an excess contribution into the thermal expansion of erbium boride at low temperatures. It was determined that this contribution is due to the CEF effects on ErB 50 thermal expansion.