Perpendicular magnetic anisotropy in Co-Pt granular multilayers

Magnetization hysteresis curves have been measured on Co granular multilayers, (Al2O3/Co/Pt)(N) (N = 1 and 25), with the applied magnetic field parallel and perpendicular to the substrate plane. In all samples perpendicular magnetic anisotropy was observed. For Co particles with average diameter 3 nm, the coercive field at low temperature is mu H-0(C) = 0.5 T. H-C decreases for increasing temperature and disappears at approximate to 200 K. A soft magnetic component is also present in all samples up to the freezing temperature T-f = 365 K. Co and Pt XMCD measurements at the L-2,L-3 edges were performed, yielding to the orbital mL and spin m(S) contributions to the total magnetic moment of the system. These results, in addition to XANES ones, indicate the presence of CoxPt1-x alloy. Particles conformed of CoPt alloy, embedded in Pt and coupled magnetically by dipolar or RKKY interaction, may explain the phenomenology observed in these systems. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752096]