STRONG CLAMPING OF THE FERROMAGNETIC TRANSITION IN EPITAXIAL ER

We report the magnetization behavior of single-crystal epitaxial films of Er lattice matched to YxLu1-x alloy substrates. As the Er is large ly strain-free, the main epitaxial constraint on its ferromagnetic tra nsition arises solely from the interaction of the magnetostriction wit h the clamping effect of epitaxy. We observe large modifications of th e magnetic behavior which establish that the clamping effect is large. The very different epitaxial behaviors of Dy and Er are explained in terms of accessible domain structure.