MAGNETIC-PROPERTIES OF RF DIODE SPUTTERED COXFE100-X ALLOY THIN-FILMS

The systematic variations in the magnetic properties of as-deposited ( by RF diode sputtering) and annealed CoxFe100-x (x=0, 15, 50, 67, 90, 100) alloy thin films mere studied in this work. Maximum values of 4 p i M(s) (21.3 kGauss) and H-c (253 Oe) were observed in as-deposited fi lms with, respectively, x=15 and x=50. Films with 0 less than or equal to x less than or equal to 15 had rotatable hysteresis loops with squ areness S approximate to 1. With increasing Co, S decreased and the fi lms became isotropic. Large decreases in H-c and resistivity, and larg e increases in 4 pi M(s) were produced in films with x=50 and 67 by an nealing in vacuum at 370 degrees C, in the presence of an in-plane fie ld. The in-plane anisotropy of the annealed films had a complex biaxia l symmetry. A similar biaxial anisotropy was observed in Co90Fe10 film s deposed in an approximate to 200 Oe planar field. This anisotropy wa s observed independent of whether the substrate ws crystalline Si, gla ss or polyimide. Thus the biaxial anisotropy could not be ascribed to structural constraints at the film-substrate interface, but was probab ly induced in the film during depositon. The optimum binary CoFe alloy films for application at GHz frequencies require highly oriented unia xial anisotropies. For reasons not fully understood, it was not possib le to obtain well oriented as-deposited, or annealed, binary CoFe film s with uniaxial anisotropy.