Step induced slanted perpendicular magnetic anisotropy in 4-miscut Si(111)/Cu/Au/Co/Au system

초록

Recently, rich magnetic properties have been found in various novel systems, and the study on the magnetic anisotropy in artificial nano-structures is currently a very challenging problem. The magnetic anisotropy is important not only for application, but also for the fundamental physical understanding of low dimensional magnetic systems. A good example is perpendicular magnetic anisotropy found in very thin magnetic layers on certain substrates. For such nanometer-thick magnetic layers the magnetic anisotropy strongly depends on thickness, with the spins reorienting from perpendicular to in-plane or vice verse beyond a certain thickness[1]. It is now well known that the perpendicular magnetic anisotropy is very sensitive function of the substrate, buffer layer, overlayer, roughness, and crystalline orientation[2]. We have investigated the magnetic anisotropy of molecular beam epitaxy (MBE)-grown Si(111)/Cu/Au(2ML)/Co(5ML)/Au on 4-miscut wafers with Brillouin light scattering (BLS) and magneto-optical Kerr effect (MOKE) measurements. Since the small magnetic signal from a few monolayer thick magnetic layer, we employed MOKE and BLS measurements to study the magnetic anisotropy of the ultra thin Co films. We obtained MOKE and BLS data for various orientations of in-plane applied magnetic field with respect to the miscut direction, and we compared the results with the Stoner-Wolhfarth (SW) single domain model. From this analysis we find that the easy axis orientation of the Co layer in this system is neither perpendicular nor in-plane : the easy axis orientation is slightly slanted from the film normal to the miscut direction. Since there is no such slant magnetic anisotropy on the non-miscut Si system, and the direction of the incline of the magnetic anisotropy is strongly correlated with the direction of the miscut, we conclude that the slant magnetic anisotropy is due to the steps in the 4 -miscut Si(111) substrate.