Multicamadas magnéticas e pseudoválvulas de spin com anisotropia perpendicular sobre substratos nanoestruturados

Abstract

Co/Pd multilayers and [Co/Pd] / Co / (Pd or Cu)/ [Co/Pd] pseudo spin-valves (PSV) with different configurations have been grown by dc magnetron sputtering technique onto glass substrate and different nanostructured anodic aluminum oxide (AAO) substrates (dots or antidots). Structural characterization has been made by x-ray diffraction and x-ray reflectometry, and image characterization has been performed using atomic force microscopy and scanning electron microscopy. Magnetic behavior has been measured using an alternating gradient field magnetometer and the surface magnetization has been imaged by magnetic force microscopy. Extraordinary Hall effect and magnetoresistance transport measurement played an important role in this work. The behavior of the magnetic reversion in the multilayers is dependent of the cobalt thickness, and for thicknesses smaller than 4Å the magnetization remains perpendicular to the surface of the sample. The inversion in the PSV magnetization is characterized by two phases, a consequence of the decoupling between the multilayers that is strongly dependent on the thickness of the spacer and the number of repetitions of the Co/Pd. The coercivity of films grown onto AAO membranes is greater than that of continuous films because of the greater number of imperfections that act as pinning points for the magnetic domains. An evolution in magnetoresistance values was obtained as a function of the thickness of the spacer and number of Co/Pd bilayers. Anomalous peaks in the Hall effect measurements in PSVs show the possibility of applications in non-volatile magnetic storage systems.