Crystal field effects on the magnetic structures of the rare earth compounds with the FeB structure

In order to confirm the role of the crystalline electric potential on the stability of non collinear magnetic structures of the rare earth compounds with the FeB-type structure, the magnetic properties of the (Gd_0.5Y_0.5)Ni compound, where the rare earth orbital moment is nul, are studied. Below its Curie temperature (57 K) the compound is ferromagnetic. The spontaneous magnetization at 0 K reaches 7.05 μ_B per gadolinium atom. Yttrium and nickel atoms being not magnetic the gadolinium moments are parallel and the exchange interactions are positive. Then the non collinear magnetic structures observed when the alloyed rare earths have an orbital moment result from the competition between a multiaxial anisotropy due to the crystal field effects and isotropic exchange interactions of the Heisenberg type.