Growth temperature dependence of biquadratic coupling in Fe/Cr(100) superlattices studied by polarized neutron reflectivity and x-ray diffraction (abstract)

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We have measured the polarized neutron specular reflectivity of superlattices of nominal composition (5.0 nm Fe/1.7 nm Cr) grown by molecular-beam epitaxy. This chromium thickness lies at a minimum of the oscillatory bilinear (180°) coupling parameter, so these films are especially sensitive to biquadratic (90°) terms. One set of films was grown at a substrate temperature of 293 K and another at 593 K. Using neutron reflection, we find that the films grown at 523 K exhibit a 90° magnetic moment rotation between successive Fe layers, while the 293 K films are remanently ferromagnetically ordered in small applied fields (H=1.7 mT). Furthermore, we have observed that films grown at elevated temperature exhibit a larger amount of diffuse x-ray scattering due to conformal roughness than those grown at room temperature. These results suggest that the biquadratic coupling could be induced by the structure of the interfaces. We will also present the field and temperature dependence of the neutron reflectivity from the biquadratic films. Journal of Applied Physics is copyrighted by The American Institute of Physics.