MOSSBAUER STUDIES OF THE SURFACE AND BULK PROPERTIES OF SUBSTITUTED IRON-GARNET FILMS IN THE VICINITY OF THE CURIE-POINT

The magnetic properties of the surface layer and bulk of iron-garnet f ilms of composition Y2.6Sm0.4Fe3.7Ga1.3O12, grown by liquid-phase epit axy on substrates of a gadolinium-gallium garnet single crystal, are i nvestigated. The method of simultaneous gamma-ray, x-ray, and electron Mossbauer spectroscopy is used for the investigations. It is found th at the temperature T-c(L) of the transition to the paramagnetic state of a thin layer localized at a depth L below the surface within simila r to 300 nm decreases smoothly with decreasing distance from the surfa ce. The causes of the difference between the temperature of the transi tion to the paramagnetic state in the surface layer and that bulk of t he film are: I) variation of the degree of substitution of gallium for iron in the surface layer; 2) weakening of exchange interactions at t he surface of the sample. (C) 1997 American Institute of Physics.