SIZE EFFECT ON GIANT MAGNETORESISTANCE OF CO-AG FILMS

For Co-Ag sputtered alloys, magnetization and magnetoresistance (MR) c urves are divided into ferromagnetic and superparamagnetic components, and the radius of the superparamagnetic Co grains, r(g), and the dist ance between the Co grains, r,, are estimated analytically from the ma gnetization curves of the superparamagnetic component. The MR of the s uperparamagnetic component, Delta rho(SP), is proportional to the dens ity of grains or it is given by Delta rho(SP) = kr(g)(3) exp(-t(g)/l) with k = 3.8 x 10(19) Omega/m(2) and l = 20 Angstrom, suggesting that the giant MR occurs mainly in the inner part of superparamagnetic Co g rains.