Mechanisms controlling magnetic properties of pseudobinary compounds TbNi5-xMx (M=Cu or Al)

Magnetic properties and heat capacity of the pseudobinary TbNi5-xCux and TbNi5-xAlx alloys have been studied for x≤2.5 and x≤1.5, respectively. The substitution of Cu or Al for Ni decreases sharply the spontaneous magnetic moment, increases the magnetic anisotropy in the 'easy' basal plane, and leads to strong magnetic domain wall pinning. The Curie temperature TC in TbNi5-xCux depends on x non-monotonously and has a maximum value at x=1, while TC in TbNi5-xAlx does not depend on composition up to x=1 and sharply decreases at x>1. These results are explained by the effects of random local crystal fields, band magnetism and heterogeneous polarization of the mixed 3d band