Crystal structure and magnetic properties of V-doped YCo 2 and YCo 3 and their hydrides

Abstract

Pseudo-binary YCo 3− x V x and YCo 2− x V x ( x = 0.1 and 0.2) phases have been investigated for the influence of V-doping on the crystal structure and magnetic properties of YCo 3 (PuNi 3-type, space group R 3 ¯ m ) and YCo 2 (MgCu 2-type, space group F d 3 ¯ m ) and their hydrides. All substituted solid solutions preserve the structure of the binary parent compounds. The lattice parameters increase with increasing V content. All investigated compounds and solid solutions can easily absorb hydrogen up to 3.2–3.9 at.H/f.u. at room temperature at 0.1–0.12 MPa pressure without amorphization. YCo 3 and solid solutions YCo 3− x V x show ferrimagnetic behaviour where Co/V substitution reduces T c from 301 K of YCo 3 to 225 K in YCo 2.8V 0.2. Hydrogenation causes complex antiferromagnetism below 200 K in the γ-phase hydrides with a reduced mean 3d-moment at low temperatures. Substitution of Co by V induces weak ferromagnetism in the archetypical itinerant electron metamagnet YCo 2 with Curie temperatures of 175 K and 110 K and a mean 3d-moment of 0.14 μ B and 0.07 μ B at 6 T and 2.5 K for x = 0.1 and x = 0.2, respectively. Hydrogen absorption enhances the mean 3d-moment slightly but reduces the ordering temperature to below 30 K in the corresponding β-phase hydrides. A ferromagnetic background occurs in all YCo 2 and YCo 3 based hydrides persisting up to above room temperature which is of different origin but appears to be not an intrinsic property of these hydrides.