Perpendicular Magnetic Anisotropy and Giant Magnetoresistance of Co-Au Alloyed Films

Abstract

Co-Au granular films have been prepared on glass substrates by rf sputtering. The magnetization curve exhibits the superparamagnetic and ferromagnetic natures. When the Co composition, x, decreases, the superparamagnetic nature increases, and the giant magnetoresistance (MR), which comes mainly from the superparamgnetic granules, increases up to about 2.5 % at x '" 23 at%. When the film is annealed, the granules grow keeping the superparamgnetic nature, and so the change in the resistivity, L!p, is held almost constant up to 250•C. The MR ratio increases on annealing and shows the maximum value of about 2.5% at 300•C. Annealing above 300•C causes the magnetism change from the superparamagnetic to the ferromagnetic due to the grain growth above the critical size, resulting in the decrease of L!fY. Furthermore, the growth of the ferromagnetic (Ill) oriented Co grains causes the increase in the perpendicular anisotropy.