Magnetic properties of Terbium-Scandium Alloys

Abstract

Measurements have been made of the lattice parameters, density and magnetic characteristics of a series of alloys between Terbium and Scandium. Both single crystal and poly-crystalline materials have been used in this investigation. It is found that the lattice parameters show a slight deviation from Vegard's Law. The Neel temperatures follow a T(_N)OCG(^1.33) dependence unlike the rare earth metals and other alloy systems, where a T(_N)OCG(^0.66) law is obeyed.(G=effective de Gennes function). The paramagnetic Curie points show an approximate dependence on G(^-2) unlike the θ(_ρ)ϬĞ variation observed for the rare earth metals and the alloys with Yttrium. Thermal expansion and magnetostriction measurements have been made along the principal directions of single crystals of alloys of composition T(^b)0.89(^sc)0.11 and Tb(_0.825)(^sc)0.175. An estimate of the exchange constants and their derivatives has been made for the alloy T(^b)0.89(^sc)0.11 with the help of the turn angle data provided by Dr. H,R, Child. The contribution of magnetostrictive energy has been estimated in the two alloys following Cooper's analysis. It is observed that the magnetostrictive energy drops rapidly with composition and this is assumed to be the cause of the absence of ferromagnetism even in materials containing fairly high proportion of Terbium.