Investigation of an 18 Å Al 2O 3 layer in a magnetic multilayer system by Rutherford and resonant scattering

Abstract

Spin tunnel junctions, consisting of a metallic multilayer with a thin insulating buffer layer, in most cases Al 2O 3, show a large tunneling magnetoresistance (TMR) and are therefore of high interest for future magnetic read heads and non-volatile memories. The properties of these junctions are strongly influenced by the quality of the insulating buffer layer and its behavior during thermal treatment. Measurements with conventional RBS using devices in the as-deposited state and after different heat treatments at temperatures up to 200°C revealed changes in the stoichiometry and O distribution in the buffer layer that can be correlated with changes in the respective magnetic properties. The application of the 16 O( 4 He, 4 He) 16 O resonant scattering resonance with incident energies ranging from 3.01 to 3.35 MeV enabled the separate profiling of O in all parts of the sample: the partly oxidized sample surface, the aluminum oxide layer and the silicon dioxide layer covering the Si substrate. Simulations of the energy dependence of the O scattering yield showed that the oxygen is fully retained in the aluminum oxide buffer layer and no diffusion into adjacent metallic layers has occurred. The results indicate also that even Al 2O 3 layers with significantly lower thicknesses can be profiled with this method.