Abstract
We have investigated the spin Seebeck effect (SSE) generated by current induced-heating in ultra-thin yttrium iron garnet film (20 nm) covered by an 8 nm thick Pt layer. By passing current in the Pt layer, an out-of-plane temperature gradient is established that, in turn, generates an out-of-equilibrium magnons population. The resulting pure spin current is detected using the inverse spin Hall effect (ISHE) measured in the Pt electrode. A lock-in detection scheme is used to separate the SSE signal from other magneto-galvanic effect. Indeed, the SSE signal is obtained as the second harmonic voltage response, while spin Hall magnetoresistance (SMR) is measured as the first harmonic response to the ac excitation current. Interestingly, the amplitude of the SSE in such thin YIG film is comparable to what has been reported for much thicker films.
Highlights
Caloritronics has become a field of intense interest as it holds promise to advantageously use what is usually considered as wasted thermal energy to create and manipulate spin information.[1]
A study of inverse spin Hall effect (ISHE) voltage on a Pt layer deposited on a 20 nm thick Yttrium Iron Garnet (YIG) film
The results reported by other groups show similar values for the spin Seebeck effect (SSE) signal in thin YIG/Pt systems.[13,18]
Summary
Caloritronics has become a field of intense interest as it holds promise to advantageously use what is usually considered as wasted thermal energy to create and manipulate spin information.[1] Thermal gradients, through the generation of out-of-equilibrium chemical potential profiles, have the ability to give rise to pure spin currents, which is interesting notably in case of insulating ferromagnets like Yttrium Iron Garnet (YIG).[2] The key phenomenon in caloritronics is the spin Seebeck effect (SSE),[3] and some SSE experiments have been performed on magnetic metallic systems such as Permalloy.[4,5] in ferromagnetic metals, there are a number of thermo-electric effects (such as anomalous or planar Nernst effect) that can bring artefacts in the quantitative interpretation of the SSE. By considering an electrical insulator ferromagnet such as the low damping YIG,[6,7,8] the SSE signal can be more detected without any charge induced thermal effects. A study of ISHE voltage on a Pt layer deposited on a 20 nm thick YIG film
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