Magnetic and magnetoelastic properties of epitaxial (2Â 1Â 1)-oriented RFe2 (R=Dy, Tb) thin films

Epitaxial, (2 1 1)-oriented thin films of RFe2 (R: rare earth; here: Dy, Tb) were deposited by molecular beam epitaxy on faceted and non-faceted α-Al2O3 (101¯0) (m-plane) substrates utilizing a 15 Å thin Fe seed layer and a 500 Å Nb buffer layer. Detailed X-ray diffraction analyses revealed a twin-free epitaxial (2 1 1)-oriented growth of buffer layer and film. The magnetostrictive layer RFe2, as well as the template layers Nb and Mo exhibited the same crystallographic in-plane orientation with regard to the substrate. The same epitaxial relationship was found for films prepared on faceted and on non-faceted substrates. This implies a coherent crystal overgrowth of the epilayers over the facet ridges. Magnetization measurements of the RFe2 films revealed coercive fields of 0.4 T for TbFe2 and 0.13 T for DyFe2. The magnetoelastic coefficients at 1.1 T amounted to b=-107MPa and b=-37MPa for the TbFe2 and DyFe2 thin films, respectively.