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arXiv · 2508.02492

Theory of nonlinear magnetoelectric transport effects in normal-metal $-$ magnetic-insulator heterostructures

Oliver Franke·Piet W. Brouwer
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Abstract

Heterostructures of normal metals (N) and magnetic insulators (F) show paradigmatic effects, such as spin-Hall magnetoresistance and electric drag currents. These effects are linear in the applied electric field $E(\omega)$. Normal-metal $-$ magnetic-insulator heterostructures also exhibit a characteristic nonlinear response quadratic in $E(\omega)$, referred to as unidirectional spin-Hall magnetoresistance or spin-torque diode effect. In this article, we develop a theory of the bilinear response of FN bilayers and NFN trilayers for finite frequencies $\omega$ of the driving field and for four contributions that have been previously considered in the literature: Joule heating, phonon-mediated unidirectional magnetoresistance, the spin-torque diode effect, and magnonic unidirectional spin-Hall magnetoresistance. We identify their distinct dependencies on frequency and the magnetization direction of the magnetic insulator and examine their scaling with magnetic field and system geometry, providing a framework for experimental differentiation.

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Oliver Franke, Piet W. Brouwer. 2025-08-04. Theory of nonlinear magnetoelectric transport effects in normal-metal $-$ magnetic-insulator heterostructures. https://doi.org/10.1103/h2dw-w3xg

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