Features of the magnetic properties of Co/Si/Co thin-film systems

Abstract

The physical properties of thin magnetic films of 3d transition metals and multilayer structures consisting of alternating submicron thick magnetic and non magnetic layers are still among the most interesting objects for investigation in the physics of magnetic phenomena. The interest in these investigations is related, in particular, to the wide use of these systems in numerous devices of modern micro and nanoelec tronics based on the discovery of phenomena such as colossal magnetoresistance [1], antiferromagnetic exchange coupling between magnetic layers via non magnetic spacers [2], and oscillating exchange cou pling between ferromagnetic layers (Fe, Co) via non magnetic metal (Cu, Ag, Au, Mo, Ta, etc.) spacers [3,4]. Quantitative evaluation of the oscillating exchange coupling between magnetic layers in thin film systems as dependent on the thickness of a nonmagnetic metal interlayer is usually based on the Ruderman-KittelKasuya-Yosida mechanism (RKKY interaction) and takes into account the quantum confinement effects [5,6], which are manifested by changes in the electron structure of ultrathin magnetic layers (the appearance of so called quantum well states) as compared to that of volume materials.Despite considerable progress in investigation of the aforementioned materials, the physics of exchange interactions in thin film magnetic structures with semiconductor spacers is far from complete under standing of the observed phenomena. The most inter esting experimental investigations of the structural and magnetic properties have been reported for Fe/Si [7⎯11] and Co/Si [10][11][12][13][14][15][16][17][18][19] thin film systems. Analysis of the available data showed that the antiferromagnetic exchange between iron layers in Fe/Si/Fe systems was observed for silicon layer thicknesses within 1.4-1.7 and 1.4-2.2 nm (see, e.g., [20,21]). However, data on the exchange interaction between magnetic layers via nonmagnetic spacers in Co/Si/Co thin film systems are rather contradictory. At the same time, it is known that magnetic transition metals (Fe, Co) are widely used in multilayer structures possessing colossal mag netoresistance, while silicon is a base element for modern micro and nanoelectronics. Thus, the study of magnetic properties of systems consisting of mag netic metal layers with Si spacers is of special impor tance.This Letter presents the results of an investigation of the properties of Co/Si/Co thin film systems. In order to provide deeper insight into the behavior of Co/Si/Co trilayers in a magnetic field, we have thor oughly studied the influence of the thickness of silicon interlayer on these magnetic characteristics of sam ples.The experiments were performed with Co/Si/Co three layer structures grown by sequential magnetron sputter deposition of Co and Si layers onto glass sub strates at room temperature. The samples were pre pared in a vacuum chamber with a residual pressure of 3.8 × 10 -7 mbar. The working gas (argon) pressure dur ing sputtering was on the order of 3.8 × 10 -3 mbar. The thicknes...