Influence of hydrogen on structural and magnetic properties of the hexagonal Laves phase HoMn2

Abstract The HoMn 2 compound crystallizes in the cubic C15 or hexagonal C14 Laves phases depending on preparation. The effect of hydrogen absorption on structural and magnetic properties of HoMn 2 H x hydrides for the C14 phase has been investigated by XRD and AC/DC magnetometry in the temperature ranges of 75–380 K and 4–390 K, respectively. In addition to general features revealed by R Mn 2 H x compounds ( R =rare earth or Yttrium), unusual behavior of these hydrides was found. In particular, a transformation from the hexagonal to the monoclinic structure was detected, the same as that observed for cubic HoMn 2 H x compounds. The structural transformations are correlated to the magnetic behavior. The presented results are compared mainly with the properties of the cubic HoMn 2 H x hydrides as well as with those of other R Mn 2 H x hydrides. Tentative magnetic and structural phase diagrams are proposed.