Influence of hydrogen absorption on magnetic ordering in some zirconium-based Laves phase compounds

Magnetization measurements were carried out on several zirconium-based hexagonal Laves phase compounds, i.e. the ZrMnsub(2+delta), (Zr,Ti)Mn2, Zr(Mn,Fe)2 and Zr(Fe,Al)2 systems and their hydrides. The absorbed hydrogen leads to a large increase (20%-30%) in volume without a change in the crystal structure. ZrMnsub(2+delta) is a weak Pauli paramagnet but becomes a spin glass near-ferromagnet by hydriding, indicating that the manganese moments are subjected to competing ferromagnetic and antiferromagnetic coupling tendencies. In the (Zrsub(1-x)Tisub(x))Mn2 hydrides, ferromagnetic, spin-glass-like, ferromagnetic and antiferromagnetic behaviors appear at 4.2 K in the sequence of increasing x and/or decrease in hydrogen concentration. In the Zr(Mn,Fe)2 system, the hydrogen absorption increases both the magnetic moments and the magnetic transition temperatures, while absorbed hydrogen leads to suppression of ferromagnetism in the Zr(Fe,Al)2 system. These varied and complex magnetic behaviors are attributed to the effects of (1) variations in the interatomic distances, (2) changes in the 3d electron concentration and (3) varying local hydrogen concentrations occurring as a result of statistical fluctuations. (Auth.)