Enhancement of Spin-Seebeck Voltage by Spin-Hall Thermopile

Abstract

Voltage signals induced by the spin-Seebeck effect (SSE) are shown to be enhanced by introducing a thermopile structure consisting of two different metals with positive and negative spin-Hall angles. In the “spin-Hall thermopile”, the positive and negative SSE signals in the metals are added to the output voltage in series. Here, we demonstrate that a Pt/Nb thermopile on an Y3Fe5O12 (YIG) slab exhibits the SSE voltage one order of magnitude greater than that in a plain Pt/YIG system. Since the spin-Hall thermopile enables sensitive detection of a spin voltage in a versatile manner, it will be useful to construct spin and heat sensors.

Temperature dependence of spin diffusion length and spin Hall angle in Au and Pt

“…Despite the extensive theoretical debate on the magnitude of the individual mechanisms in different metals [16][17][18], accompanied by experimental work [19][20][21], the quantitative role of each contribution for any specific system often remains unclear. Nevertheless, the interest into the SHE is clear: spin currents can be generated and detected without using either ferromagnetic (FM) electrodes nor applying an external magnetic field, resulting in a great technological advantage [22,23]. Understanding the underlying physics of the effect to search for materials that provide a large effect has thus become an important topic in spintronics.…”

Temperature dependence of the spin Seebeck effect in [Fe3O4/Pt]n multilayers

“…Different possibilities are currently being explored, 21 such as increasing the spin current detection efficiency by taking advantage of the spin Hall angle characteristics of different N materials, [22][23][24][25] as it was shown by the implementation of spin Hall thermopiles. 26 However, using this approach increases the thermoelectric voltage at the expense of the extractable electrical power due to increased internal resistance of the thermopile devices. 27 Other approaches can be directed towards increasing the thermal spin current generation, as recently shown in spin induced thermoelectric measurements in magnetic multilayers.…”

Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

“…However, the SSE reported up to now is small [23]. One approach for the improvement of the observed signal is aimed at the enhancement of the spin current detection, by exploiting the spin Hall angle characteristics of the N layer [24], and one * ramosr@imr.tohoku.ac.jp such example is the SSE voltage enhancement in spin Hall thermopiles [25], however, there is no power improvement associated with the voltage increase [26] due to the large internal resistance of these devices. Another possibility to increase the SSE voltage could be directed towards an increase of the generated spin current.…”