Evolution of magnetism in Tb(CoxNi1−x)2B2C

AbstractThe magnetic properties of polycrystalline Tb(CoxNi1−x)2B2C (x=0.2,0.4,0.6,0.8) samples were probed by magnetization, specific heat, ac susceptibility, and resistivity techniques. For x≠0.4, the curves obtained are consistent with the features expected for the corresponding magnetic modes, namely k1=(0.55,0,0) at x=0; k2=(12,0,12) at x=0.2 and 0.4; k3=(0,0,13) at x=0.6, and k4=(0,0,0) at x=0.8 and 1. For each of these compositions, we thoroughly discuss the analyses leading to the determination of the magnetic critical temperature through separate independent measurements. For x=0.4, even though neutron diffraction indicates a k2 mode (but with a reduced magnetic moment) the magnetization, the ac susceptibility, and resistivity indicate two magnetic events, in sharp contrast with other concentrations, for which a single critical event is observed; furthermore, deviation from Curie–Weiss behavior is observed below 150K for this sample. These features, together with the evolution of both magnetic moment and critical temperature, are attributed to a combination of crystalline electric field effects and an interplay between competing magnetic couplings