Photo-spin voltaic effect and photo-magnetoresistance in proximized platinum

Abstract

Spin orbit coupling in heavy metals allows conversion of unpolarized light into an open-circuit voltage. We experimentally prove that this photo-spin voltaic effect is due to photo-excitation of carriers in the proximized layer and can exist for light in the visible range. While carrying out the experiment, we discovered that, in closed-circuit conditions, the anisotropic magnetoresistance of the proximized metal is a function of the light intensity. We name this effect photomagnetoresistance. A magneto-transport model is presented that describes the change of magnetoresistance as a function of the light intensity. arXiv:1708.04130v2 [cond-mat.str-el]

Photo-spin-voltaic effect in PtMn/Y3Fe5O12 thin films

“…Ellsworth et al [13] measured the PSV voltage in the infrared region in the Pt layer proximized by YIG. Similarly, Li and Ruotolo [2] experimentally showed that the PSV effect also existed in the visible range. In addition, they demonstrated that the AMR of the proximized layer is light-dependent.…”

“…In ultra-thin PtMn films, the Nèel temperature was measured to be below room temperature. Yet, like ultra-thin Pt films on YIG, a proximity effect exists near the interface and a magnetization arises in the metal over depths of ∼0.5 nm [2].…”

“…Figure 6 shows the open-circuit voltage at room temperature generated under light illumination with intensity i = 0.4 W for the devices A, B, and C. It is important to point out that the lamp used in this experiment was a 'cold' bulb lamp with a heat absorbing filter that diffused broad light with low power density, and not a collimated laser like those used in experiments for a light-induced spin-Seebeck effect and the anomalous Nernst effect [27]. Moreover, measurements at temperatures down to 10 K reported on a similar system (Pt/YIG) [2] by one of the authors have demonstrated that the transverse voltage detected in our experimental setup does not change when the sample is sitting on a cold finger; therefore, the measured voltage did not depend on the transverse gradient of temperature [2]. No voltage signal was measured on device D, possibly because the PtMn layer was too thin and was noncontinuous.…”

“…Electrons carry charge as well as spin angular momentum, hence electrons can be discriminated based on unlike spins. Imbalance between the spins pointing in opposite directions, i.e., spin up and spin down, can lead to the different phenomena including the quantum spin Hall effect [1], whereas the separation between the electrons (spin accumulation) can be realized by the inverse spin-Hall effect (SHE) [2,3]. More importantly, electrons with opposite spins can be driven in opposite directions.…”

“…For the detection of pure spin currents, M Aldosary et al [6] and H Kurebayashi et al [7] showed that spin currents can be converted in an open-circuit voltage by using the inverse spin Hall (ISH) effect, which appears in metals with large spin-orbit coupling (SOC). Conversely, generation of pure spin currents can be achieved by resorting to various methods such as spin pumping driven by microwave field excitation of the magnetization [1,2], and the spin Seebeck effect due to a temperature gradient [8,9]. S M Rezende et al [10] proposed the magnon spin-current theory for the longitudinal spin-seeback effect in nonmagnetic (NM)/ferromagnetic insulator (FMI) (Pt/YIG) bilayers.…”