Magnetic properties of hydrogen-amorphized RCo 2H x (R = Gd, Tb, Dy, Ho, Er, Tm and Y) alloys

Abstract

High-field magnetization curves and temperature dependences of the magnetization have been measured for RCo 2H x alloys amorphized by hydrogen treatment (R = heavy rare earths and yttrium). It was found that am-RCo 2H x are ferrimagnets with a strong Co–Co and a relatively weak R–Co exchange interaction. The compensation point observed in the M( T) curves shifts systematically to lower temperatures with increasing atomic number of the R elements. Both magnetic moment and compensation temperature depend on the amorphization temperature, which indicates a metastable and heterogeneous structural state of the amorphous hydrides. For the compositions with anisotropic R ions (Tb, …, Tm) the calculated magnetic moment of the R subsystem appears to be considerably lower than the value g J J μ B for corresponding rare earth ions, probably due to a non-collinear magnetic structure of the R subsystem. From the pressure effect on the magnetization measured for am-HoCo 2H 3, the magnetoelastic coupling constant is estimated as C dd = 0.5 × 10 −3 (μ B/Co) −2, the value being considerably lower than that for parent RCo 2 compounds.