Strong Interfacial Exchange Field in a Heavy Metal/Ferromagnetic Insulator System Determined by Spin Hall Magnetoresistance.

Gomez-Perez, Juan M; Zhang, Xian-Peng; Calavalle, Francesco; Ilyn, Maxim; González-Orellana, Carmen; Gobbi, Marco; Rogero, Celia; Chuvilin, Andrey et al. · Nano Lett · 2020

basic_science · Level V

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Abstract

Spin-dependent transport at heavy metal/magnetic insulator interfaces is at the origin of many phenomena at the forefront of spintronics research. A proper quantification of the different interfacial spin conductances is crucial for many applications. Here, we report the first measurement of the spin Hall magnetoresistance (SMR) of Pt on a purely ferromagnetic insulator (EuS). We perform SMR measurements in a wide range of temperatures and fit the results by using a microscopic model. From this fitting procedure, we obtain the temperature dependence of the spin conductances (<i>G</i><sub>s</sub>, <i>G</i><sub>r</sub>, and <i>G</i><sub>i</sub>), disentangling the contribution of field-like torque (<i>G</i><sub>i</sub>), damping-like torque (<i>G</i><sub>r</sub>), and spin-flip scattering (<i>G</i><sub>s</sub>). An interfacial exchange field of the order of 1 meV acting upon the conduction electrons of Pt can be estimated from <i>G</i><sub>i</sub>, which is at least three times larger than <i>G</i><sub>r</sub> below the Curie temperature. Our work provides an easy method to quantify this interfacial spin-splitting field, which plays a key role in emerging fields such as superconducting spintronics and caloritronics as well as topological quantum computation.