THE MAGNETIC PHASE-TRANSITION OF A LATTICE-MATCHED HOLMIUM THIN-FILM

Neutron and x-ray scattering measurements have been made of the magnet ic phase transition in a thin single-crystal film of holmium. The 5000 Angstrom film was grown on a seed of a lutetium and yttrium alloy wit h a concentration chosen such that the basal plane was lattice matched to the holmium film. It was capped by 10 000 Angstrom of a similar fi lm. The measurements below T-N gave the critical exponent beta = 0.37 +/- 0.03. Above T-N the scattering suggests that the anomalous long-le ngth-scale scattering is at least 20 times weaker than has been observ ed in similar experiments on bulk and thin-film holmium. These results show that the long-length-scale scattering is associated with the cry stallographic surface rather than the end of the magnetic layer. The i mplications of this result for the origin of this type of scattering a re discussed.