Hyperfine-field spectrum of epitaxially grown bcc cobalt

Abstract

The hyperfine-field spectrum of the bcc phase of a 357-romanÅ-thick metallic cobalt film, epitaxially grown on a GaAs substrate, has been determined by spin-echo nuclear magnetic resonance. The peak of the distribution of hyperfine fields in bcc Co occurs at 167 MHz, much lower than the value found for fcc Co (217 MHz), suggesting that the moment in the bcc phase is lower than that of the fcc phase, in agreement with the measurements of Prinz, but in disagreement with recent theoretical calculations (assuming that no significant structural differences exist between theory and experiment). The full width of the distribution is 75 MHz, seven times greater than that found in thin fcc Co films. X-ray rocking-curve measurements yield a linewidth of 118 arc seconds, implying too low a dislocation density to explain the observed NMR line broadening.