Nonlocal detection of out-of-plane magnetization in a magnetic insulator by thermal spin drag*

Recent demonstrations of efficient current-induced control of magnetization in magnetic insulators (MIs), combined with their highly tunable properties, provide fertile grounds for spintronic research and applications [1]. Despite MIs’ electrically insulating nature, the various spin transport phenomena (spin Seebeck, spin Hall, etc.) have granted us the relevant tools to detect their magnetization vector in a local geometry with simple electrical measurements [2]. It was later discovered that the MIs' magnetization vector can be detected also in a nonlocal geometry by long-distance magnon transport. However, this method is limited to the in-plane magnetization component and to films allowing long magnon diffusion. A general detection scheme in a nonlocal device geometry for the magnetization vector both in-plane and out-of-plane, and independently of the long-range magnon transport, remained a challenge for a long time.

In this work [3], we demonstrate that, by using an engineered temperature gradient, one can detect the in-plane and out-of-plane magnetization of a MI by simply measuring the transverse voltage drop across the Pt strip placed on top. This is due to a conceptually new mechanism that combines the spin currents in a Pt/MI bilayer driven by temperature gradients perpendicular and parallel to the surface generated by a single nonlocal heat source. This simple method enables the detection of the perpendicular magnetization component in an MI in a nonlocal geometry and opens up new routes towards engineering temperature gradients to generate and manipulate thermal magnons and pure spin currents.

[1] Avci, J. Phys. Soc. Jpn. 90, 081007 (2021)

[2] Braatas et al., Phys. Rep. 885, 1-27 (2020)

[3] Avci et al. Phys. Rev. Lett. 124, 027701 (2020)