Magnetic properties of HoFe6Al6H hydride: A single-crystal study

Abstract

Abstract Crystal structure and magnetic properties were studied on a single crystal of HoFe 6 Al 6 H and compared with those of the parent HoFe 6 Al 6 compound with a tetragonal crystal structure of the ThMn 12 type. Hydrogenation leads to a 1% volume expansion. HoFe 6 Al 6 is a ferrimagnet with exact compensation of the Ho and Fe sublattices magnetizations at low temperatures. Both the hydride and the parent compound display a high magnetic anisotropy of the easy-plane type, a noticeable anisotropy exists also within the easy plane with the [110] axis as the easy magnetization direction. The hydrogenation increases slightly (from 10 to 10.45 μ B ) the magnetic moment of the Fe sublattice as a result of volume expansion. It leads to a decompensation of the Fe and Ho sublattices and HoFe 6 Al 6 H has a spontaneous moment 0.45 μ B /f.u. The enhancement of the Fe–Fe intra-sublattice exchange interaction results in a higher Curie temperature ( T C ) value, 350 K in the hydride as compared to 315 K of HoFe 6 Al 6 . The Ho–Fe inter-sublattice interaction is also enhanced in the hydride. The molecular field H mol created on Ho ions by Fe sublattice is 38 T in HoFe 6 Al 6 and 48 T in HoFe 6 Al 6 H. The inter-sublattice exchange constant n HoFe is 3.8 T/μ B and 4.6 T/μ B , respectively. High-field measurements confirm the enhancement of the Ho–Fe exchange interaction in the hydride found from the temperature dependence of magnetization.