DEPENDENCE OF GIANT MAGNETORESISTANCE ON FILM THICKNESS IN HETEROGENEOUS CO-AG ALLOYS

The dependence of magnetic properties on film thickness in as-deposited Co-Ag alloys is discussed. Films ranging in Co concentration from 0 to 100 vol % Co and thicknesses between 100 angstrom and 1 mum were deposited by sputtering onto Si(100) substrates. It was found that both magnetoresistance (MR, DELTArho) and MR ratio (DELTArho/rho) increase with thickness. Resistivity (p) decreases with increasing thickness. The dependence of MR ratio on concentration of Co is not markedly different for 200 and 2000-angstrom-thick samples. Saturation magnetization is roughly constant for thicknesses greater than approximately 200 angstrom, decreasing rapidly below this cutoff. However, most of both the thin (200 angstrom) and thick (2000 angstrom) films begin showing magnetic hysteresis between 10 and 100 K. The differences in transport and magnetization properties may be ascribed to differences in film growth for thin versus thick films.