Probing and manipulating magnetic domains and domain walls in magnetic insulators by spin currents

Spin orbit coupling in normal metals (NM) can convert charge currents in spin currents and vice versa. This effect, called spin Hall effect, is ubiquitous in spintronics and typically employed for generating and detecting pure spin currents as well as for manipulating magnetic moments in thin films. Here in this seminar, I will discuss how the spin Hall effect can be employed in magnetic insulator(MI)/NM bilayers for probing the surface magnetism of MIs as well as for switching magnetic domains and driving domain walls in thin film oxides by simply applying charge currents in an adjacent NM layer.

In the first part of the talk, I will discuss the phenomenology of the spin Hall magnetoresistance (SMR) [1] and Hanle magnetoresistance (HMR) [2] effects in MI/NM bilayers and explain how these effects are related to the spin transport properties of the heterostructure and can be used for probing the surface magnetic properties of MIs. I will present a revised microscopic theoretical model of the SMR that allows for an arbitrary magnetic ordering of the surface of the MI as well as accounts for the effect of magnetic fluctuations on the magnetotransport [3]. Results obtained in diverse magnetic oxides such as in tensile-strained LaCoO₃ films [3], spinel oxide CoFe₂O₄ films [4] and antiferromagnet-Y₃Fe₅O₁₂ coupled bilayers [5-7] will be presented and discussed.

In the second part of the talk, I will show how current-induced torques can lead to deterministic magnetization switching and to domain wall motion in thin film oxides with perpendicular magnetic anisotropy such as Tm₃Fe₅O₁₂ (TmIG). I will show that interfacial Dzyaloshinskii–Moriya interaction in TmIG stabilizes Néel chiral domain walls, which can be efficiently driven by spin-orbit torques with mobility comparable or larger than in metallic ferromagnets [8].