Effect of hydrogen for the magnetic properties of iron and cobalt in PuNi3 type hydrides Y(Fe1-xCox)2.9Hy

Magnetization and Moessbauer measurements were performed for PuNi3 type alloys Y(Fe1-xCox)2.9 and their hydrides. The composition dependencies of magnetization, Curie temperature, and average hyperfine field of 57Fe in the alloys show a maximum near x=0.5, and those in hydrides decrease with increasing x. This behavior suggests that the magnetic moments of iron and cobalt are nearly the same, except for cobalt rich alloys. Numerical fitting using a Stoner theory with a parabolic band was performed. It was assumed that the alloys and hydrides are ferromagnets of 3d-band-hole with incomplete saturation. It was shown that both the exchange energy kθ and Fermi energy ε0 decrease with substitution of cobalt for iron, and that the difference in the composition dependencies of kθ/ε0 in alloys and hydrides leads to different composition dependencies of the magnetization and Curie temperature. It was shown that ε0 and kθ decrease with hydrogenation, but kθ/ε0 increases to lead magnetization increase only in YFe3. copyright 1997 American Institute of Physics