Structural and magnetic properties of Fe/Mn superlattice films and their interfaces

Abstract

Superlattice films consisting of ferromagnetic Fe and antiferromagnetic Mn were prepared by ultra-high-vacuum evaporation. The alternate stacking of BCC Fe (110) and alpha -Mn (110) lattice planes when the superlattice periods are in the range from 40 to 80 AA and the Fe and Mn layer thicknesses are equal was confirmed by X-ray diffraction. The films have fibrous textures which are composed of coherent grains of approximate dimensions of 100 AA in the film plane and 200 AA along the growth direction. The distributions in the growth orientation are within 10 degrees . Mossbauer spectra indicate that alloy layers are formed at the interface regions and that the degree of atomic intermixing is rather extensive at the interfaces, where Fe atoms are deposited on Mn layers. The thicknesses of the alloy layers are in the region of 10 AA. When Fe layers thinner than 15 AA are sandwiched by Mn layers, the structure is changed significantly because of alloying. The Mossbauer spectra show unresolved magnetic splitting, with the magnetic hyperfine field widely distributed in the range from 0 to 200 kOe (100 kOe on average). The magnetisation curve strongly depends on the external field and also on the thermal history. The properties of Fe-rich layers are similar to those of the Fe-Mn amorphous alloy and the magnetic behaviour of the multilayers is interpreted as mictomagnetism.