MAGNETIC HYPERFINE FIELDS IN FE/CO AND FE/CU MULTILAYERS

Hyperfine fields in magnetic multilayer samples of Fe/Co and Fe/Cu having equal layer thickness of Fe and Co and Fe and Cu were measured in samples having layer thicknesses in the range 10-150 angstrom by Fe-57 Mossbauer spectroscopy. Measurements were made at 290, 77 and 4.2 K. The mean hyperfine field B(hf)BAR at Fe sites in Fe/Co multilayers was found to increase with decreasing layer thickness. The mean hyperfine field at Fe sites in Fe/Cu multilayers was observed to decrease with decreasing layer thickness. The decrease in B(hf)BAR between 4.2 and 290 K was found to be much greater in Fe/Cu samples than in Fe/Co. The Mossbauer spectra are well fitted with two sextet components, one corresponding to interface Fe sites and the other to midlayer Fe sites. Analysis of the relative intensity of these components measures the interface layer thickness. The variation of hyperfine field with sample layer thickness can be well accounted for using the measured thickness of the interface layers.