GRAIN-BOUNDARY DIFFUSION AND ITS EFFECTS ON THE MAGNETIC-PROPERTIES OF CO CU AND CO CR THIN-FILM BILAYERS

X-ray photoelectron spectroscopy has been used to investigate grain bo undary diffusion of Cu and Cr through 1000-angstrom-thick Co films in the temperature range of 300-400-degrees-C. Grain boundary diffusiviti es were determined by modeling the accumulation of Cu or Cr on Co surf aces as a function of time at fixed annealing temperature. The grain b oundary diffusivity of Cu through Co has a diffusion coefficient D0,gb of 2x10(4) cm2/s and an activation energy E(a,gb) of 2.4 eV. Similarl y, Cr grain boundary diffusion through Co thin films exhibits a D0,gb of 6x10(-2) cm2/s and an E(a,gb) of 1.8 eV. The Co film microstructure has been investigated before and after annealing by x-ray diffraction and transmission electron microscopy. Extensive grain growth and text uring of the magnetic film occurred during annealing for Co deposited on a Cu underlayer which is believed to influence the grain boundary d iffusion process. In contrast, the microstructure of Co deposited on a Cr underlayer remained relatively unchanged upon annealing. The diffe rence in grain growth between the two bilayers has been suggested to a ccount for the large disparity in activation energies. Magnetometer me asurements have shown that increased in-plane coercivity H(c), reduced remanence squareness S, and reduced coercive squareness S result fro m grain boundary diffusion of Cu and Cr into the Co films.