Site preferences for Nd in YAG films grown by LPE

We have made spin-resonance measurements of the concentration on different, though crystallographically equivalent, sites, of Nd³⁺ dilutely incorporated into thin films of yttrium aluminum garnet (YAG). The films were grown on {001}, {110}, and {111} substrates of pure YAG by liquid phase epitaxy (LPE). Sites which differ only in the orientation of their local axes relative to the growth direction are found to be unequally populated. The site preferences found for {110} films are close to, though larger than, those found previously for {110} facets of bulk crystals grown from the flux. This result supports the view that the growth-induced magnetic anisotropy of LPE films of mixed rare earth iron garnets arises from the same site preference mechanism as the anisotropy found under natural facets of bulk crystals. Very large site preferences, up to 4.5:1, are found in {001} films; but for {111} films they are only slight. Site preferences are not greatly affected by changes in growth temperature (850°C to 1044°C) or in overall concentration (0.1% to 5% atomic). The effective distribution coefficient varies with concentration and substrate orientation.