EFFECTS OF DEPOSITION TEMPERATURE ON THE GIANT MAGNETORESISTANCE OF AS-DEPOSITED AG-CO THIN-FILMS

Giant magnetoresistance (GMR) is reported in Ag1-xCox(x=0.26-0.53) films cosputtered on Si at 28-354-degrees-C from separate Ag and Co targets. GMR ratios (10 kOe maximum field) as high as 0.55 and 0.24 at 5 and 295 K, respectively, are achieved for the Ag0.67Co0.33 films deposited at a substrate temperature, T(s), of 125-degrees-C. The GMR ratio increases slightly when the T(s) increases from 28 to congruent-to 125-degrees-C, and decreases substantially at T(s) > 175-degrees-C. The resistivity of these films decreases monotonically with increasing T(s) and levels off to a value congruent-to 3 X of Ag at T(s) greater-than-or-equal-to 250-degrees-C. The films deposited at lower T(s) consist of essentially a metastable Ag-Co solid solution, while those deposited at higher T(s) consist of separate fcc Ag and fcc Co. The coercivity of these films increases rapidly at T(s) much greater than 125-degrees-C, consistent with the growth of single-domain ferromagnetic Co particles in this T(s) range. The T(s) dependence of GMR ratios is interpreted based on spin-dependent interfacial scattering arising from the T(s) dependence of the size and number of ferromagnetic Co particles within the electron mean free path.