Magnetic properties of epitaxial metallic superlattices

Superlattices (SL's) and films of rare-earth elements have been grown by means of molecular-beam epitaxy with both the c-axis and b-axis as the growth direction. Long range order spanning many bilayers is observed for both Er-Y and Dy-Y SL's grown along the c-axis, but not for Dy-Y SL's with b-axis growth. This is explained in terms of the anisotropy of the effective exchange interaction. Suppression of the low-temperature ferromagnetic transition is found in all SL's and in Er films grown on Y. This is analyzed in terms of the changes in magnetoelastic energy imposed by epitaxy. Preliminary results on Er films grown on Lu support this picture. The suppression of ferromagnetism permits the study of modulated phases to lower temperatures and higher magnetic fields, with new intermediate phases appearing that are stabilized by the magnetic field.