Interplay of the Kondo effect and ferromagnetism in the CeNi_xGa_4−x alloys

Abstract

The magnetic susceptibility (4.2-300 K) and heat capacity (C) (0.5-20 K) of the alloys, CeNi_xGa_4−x (x=0.5-1.1), exhibit features attributable to the interplay of the Kondo effect and ferromagnetism (T_c≃5 K). The value of C/T (where T is the temperature) shows an upturn below about 10 K for all the compositions; particularly in the case of the x=1.1 specimen, which is found to be nonmagnetic above 0.5 K, C/T increases to about 2.2 J/mol K² at 0.5 K, as if this alloy is a giant heavy-fermion material. In addition, the full magnetic entropy (R ln2) is attained only above 10 K in all alloys. This finding suggests either the persistence of the Kondo effect even in the ferromagnetically ordered state or some sort of itinerant magnetism.