Perpendicular magnetic anisotropy in Co-Pt granular multilayers
J. Bartolomé, A.I. Figueroa, L.M. García, and F. Bartolomé
Instituto de Ciencia de Materiales de Aragón, Departamento de Física de la Materia Condensada CSIC/U de Zaragoza, Zaragoza, Spain
L. Ruiz and J.M. González-Calbet
Departamento de Química Inorgánica, Universidad Complutense de Madrid, E-28040 Madrid, Spain
F. Petroff and C. Deranlot
Unité Mixte de Physique, CNRS/Thales, Route Départementale 128, 91767 Palaiseau Cedex, France, and Université Paris-Sud, 91405 Orsay (Paris), France
F. Wilhelm, A. Rogalev, and N. Brookes
European Synchrotron Radiation Facility, BP220, F-38043, Grenoble, France
Received April 20, 2012
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 μ0HC = 0.5 T. HC decreases for increasing temperature and disappears at ≈200 K. A soft magnetic component is also present in all samples up to the freezing temperature Tf = 365 K. Co and Pt XMCD measurements at the L2,3 edges were performed, yielding to the orbital mL and spin mS 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.
PACS: 75.30.–m Intrinsic properties of magnetically ordered materials; PACS: 75.70.–i Magnetic properties of thin films, surfaces, and interfaces.
Key words: magnetic thin films, magnetic multilayers, perpendicular magnetic anisotropy, platinum alloys, granular materials.