Crystal structure and magnetic properties of V-doped YCo2 and YCo3 and their hydrides

Pseudo-binary YCo3−xVx and YCo2−xVx (x = 0.1 and 0.2) phases have been investigated for the influence of V-doping on the crystal structure and magnetic properties of YCo3 (PuNi3-type, space group R3¯m) and YCo2 (MgCu2-type, space group Fd3¯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. YCo3 and solid solutions YCo3−xVx show ferrimagnetic behaviour where Co/V substitution reduces Tc from 301 K of YCo3 to 225 K in YCo2.8V0.2. 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 YCo2 with Curie temperatures of 175 K and 110 K and a mean 3d-moment of 0.14μB and 0.07μB 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 YCo2 and YCo3 based hydrides persisting up to above room temperature which is of different origin but appears to be not an intrinsic property of these hydrides.

Research highlights► YCo3−xVx and YCo2−xVx (x ≤ 0.2) absorb hydrogen up to 3.2−3.9 at.H/f.u. ► moderate V-doping and hydrogenation preserves the PuNi3- and MgCu2-structure types. ► Ferrimagnetism in YCo3−xVx transforms upon hydrogenation to complex antiferromagnetism. ► V doping induces weak ferromagnetism in the itinerant electron metamagnet YCo2. ► Hydrogenation of YCo2−xVx enhances the 3d-moment but reduces the ordering temperature.