Investigation of (Fe/Dy) multilayers by 57Fe Mössbauer spectrometry

The structural and magnetic properties of (Fe tFenm/DytDynm) multilayers deposited at 320 K by thermal evaporation in ultra-high vacuum (UHV) have been investigated by conversion electron 57Fe Mössbauer spectrometry (CEMS) at 300 K. These measurements enabled to determine in which conditions the perpendicular magnetic anisotropy (PMA) is optimised as a function of the layers thickness. The Fe thickness, tFe, is varied between 1 and 4 nm, and the Dy thickness, tDy, equals 1 or 2 nm. The Mössbauer spectrometry measurements reveal that the PMA is the largest when tFe is the smallest, i.e., when the multilayers are structurally close to an Fe-Dy amorphous alloy with modulation of composition.