Magnetic dipole mechanism for biquadratic interlayer coupling (abstract)

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A mechanism resulting in biquadratic interlayer coupling is proposed and analyzed theoretically. This mechanism is connected with the magnetic dipole field, created by magnetic layers with roughness. This field decays exponentially with the distance from the layer, but it shows oscillating behavior in the lateral direction. The scale of both exponential and oscillating dependencies corresponds to the scale of the interface roughness and can reach 20–30 nm. The oscillating variation of the field makes 90° alignment of the magnetization energetically favorable in analogy to the Slonczewski's mechanism. Computer simulations and estimates show that this mechanism can provide a coupling strength of the order of 0.01 erg/cm² for Fe films with 1 nm interlayer thickness. The part of the work done in Moscow and Jüelich was supported by Collaborative Research Grant CRG 921170 of the NATO Scientific Exchange Programmes. Work at UCSD was supported by the U. S. National Science Foundation. One of us (E.Ts.) is pleased to thank the Alexander von Humboldt Foundation for support. Journal of Applied Physics is copyrighted by The American Institute of Physics.