STRUCTURAL AND MAGNETIC-PROPERTIES OF EPITAXIALLY GROWN FE-SM AND FE-SM-N FILMS

Thin Fe-Sm-N films with thickness greater than or equal to 50 nm and c oercivities greater than or equal to 4 kOe were grown on an alpha-Ta ( 110) substrate by de magnetron sputtering. Transmission electron micro scopy diffraction data clearly showed that the films were polycrystall ine with the ThMn12 tetragonal structure and with a preferential orien tation of (011) Fe-Sm//(110) Ta. This resulted in a uniform distributi on of the easy axis on a cone of 29 degrees to the film normal. The st ructural data were also supported by the hysteresis loops measured as a function of angle in plane and out of plane. The high coercivity pha se was obtained from targets with 15-20 at. % Sm. For the 10 at. % Sm target, only a soft alpha-Fe phase was formed. For films of <50 nn spu ttered from 15 to 20 at. % Sm, a soft phase was clearly observed in th e vibrating sample magnetometer and was the only soft phase formed in 10 nm thick films. However, films of >50 nm thickness showed high coer civities without a kink in the demagnetization loops and seemed to be composed only of magnetically hard phase, which was probably due to st rong magnetic interactions between magnetically soft and hard phases a t the Fe-Sm/Ta interface. (C) 1997 American Institute of Physics.