Magnetism and structure of Dy/Fe multilayers studied by Fe-57 and Dy-161 Mossbauer spectroscopy

Dy(48 Angstrom)/Fe(40 Angstrom) multilayers were investigated by Fe-57 and Dy-161 Mossbauer spectroscopy in zero external field between 4.2 and 300 K. The Fe-57 spectra could be analyzed in terms of a pure bcc-Fe contribution and an intermixed interface contribution. The latter is assigned to an amorphous Dy1-xFex interface alloy with an estimated most-probable composition x approximate to 0.78. The bcc-Fe phase shows a broad spin-reorientation transition from a preferentially in-plane-oriented Fe-spin direction near 300 K to a more out-of-plane-oriented spin texture at 4.3 K characterized by an average misalignment angle of similar to 52 degrees relative to the sample-plane normal. The value of the average Dy-161 hyperfine field at 4.2 K (583.0 T) is slightly larger than the value of bulk Dy metal, but is smaller than those of Dy-Fe intermetallics. The average orientation of Dy moments which was found to be random at 4.2 K may be the reason for the misalignment of Fe magnetic moments at low temperature. The magnetic ordering temperatures of the Dy layers were determined by superconducting quantum interference device magnetometry to be T-C = 110 +/- 15 K and T-N = 200 +/- 20 K, the latter value being in agreement with that estimated from Dy-161 spectra. (C) 1996 American Institute of Physics.