Current-linear emergent induction of pinned skyrmion textures in an oxide bilayer

Abstract

Emergent electromagnetic induction (EEMI) induced through current-driven spin dynamics was recently predicted and subsequently observed in helical spin magnets, opening a new direction in spintronics and paving the way towards further miniaturization of electronic circuit elements. In contrast to conventional inductors consisting of coil-like structures whose inductance $L$ shows a linear dependence on the cross-section $A$, emergent inductors exhibit an inverse ($\propto {A}^{-1}$) proportionality, favorable for the miniaturization of electrical devices. However, the expected current-linear response of the EEMI voltage has not been demonstrated. Magnetic skyrmions hold promise as a simple platform to study the conceptual foundations of EEMI from current-driven spin dynamics. We fabricated devices of thin film bilayers of ferromagnetic SrRuO$_3$ and paramagnetic SrIrO$_3$, which are known to host interfacial N\'eel skyrmions detected by the appearance of a topological Hall-effect (THE). A large, positive and current-linear inductive response is found to accompany the THE. In our experiment, the current-induced dynamics of pinned magnetic skyrmions creates a voltage both parallel and perpendicular to the applied electric current flow, corresponding to longitudinal and transverse induction, respectively. This is the first report of transverse EEMI, indicating an angle of $80^{\circ}$ between skyrmion motion and the applied current. Our observation of current-linear longitudinal and transverse EEMI is a hallmark of pinned dynamics of magnetic skyrmion textures in oxide heterostructures.