Magnetic properties of Cr-CrH and YFe2-YFe2H4

The stronger magnetization in ferromagnetic YFe2H4 compared to YFe2 was explained by two antagonistic effects: (i) the lattice expansion due to hydrogen insertion which increases the magnetic moments MS at the Fe sites, (ii) the metal-hydrogen interaction which slightly reduces MS. In the hydride, the majority spin states of Fe are fully filled and the Fermi energy falls in a peak of the minority spin density of states. We found a small ferrimagnetic coupling of the 4d states of yttrium. Our results are in satisfactory agreement with experimental magnetic data.