Comparative study of thermal and magnetic properties of CeTyX4-y ferromagnets

Abstract

Low-temperature thermal (specific heat, CP) and magnetic [ac susceptibility, χac, and isothermal magnetization M(B)] measurements on CeTyX4−y ferromagnets (with T=Ni, Cu, Pd, Ag, Au, and X=Ga, Al, with 0.3<y<0.7) are reported. With the exception of T=Ni, all compounds with X=Ga show a typical second-order ferromagnetic transition. In the case of T=Ni, magnetic correlations set in at T≈3TC (TC being the Curie temperature) and the CP(T) and χac(T) maxima (at 3.3 and 4.2 K, respectively) do not coincide, while the M(B) curves reveal an antiferromagnetic character at lower temperatures. In these systems, the magnetic entropy of the ordered phase is larger than 85% of Rln2, in coincidence with the low values of the Sommerfeld coefficient γ<~10 mJ/mol K2. For T=Ag and X=Al, a strong diamagnetic signal was observed at Ts=0.63 K in χac(T), with the characteristics of a superconducting component. The thermodynamical properties of these compounds confirm the lack of hybridization when the Ce atom is in a ferromagnetic ground state.