The tremendous influence of hydrogenation on magnetism of NdMnGe

The hydride NdMnGeH with the tetragonal ZrSiCuAs-type of structure (P4/nmm, N129, tP8) was obtained by hydrogen absorption at 523 K and 1 MPa from the NdMnGe intermetallic compound with a the tetragonal CeFeSi crystal structure (P4/nmm, N129, tP6). Measurements of magnetization in high magnetic fields up to 60 T and heat capacity measurements reveal pronounced changes in the magnetic properties of NdMnGe after hydrogenation. The Nd sublattice changes its ordering type from ferromagnetic to the antiferromagnetic one with a more than twofold decrease of and its magnetic ordering temperature (from 199 to 84 K). We explain the observed effects by the altered exchange interactions within the Nd sublattice resulting from the changed Nd–Nd interplane distances by interstitial atoms. The results are compared with data obtained previously for the NdMn_{1- x}Ti_xGe compounds, where the Ti substitution also changes significantly the magnetic properties.