Improvement of Mixing Conductance and Spin-Seebeck Effect at Fe Interface Treatment
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Improvement of Mixing Conductance and Spin-Seebeck Effect at Fe Interface Treatment Y. Iwasaki1, M. Ishida1,2, A. Kirihara1,2, K. Ihara1,2, H. Someya1,2 K. Uchida3,4, E. Saitoh2,3,5,6, T. Murakami1, and S. Yorozu1,2 1
Smart Energy Research Laboratories, NEC Corporation, Tsukuba 305-8501, Japan 2 Spin Quantum Rectification Project, ERATO, JST, Sendai 980-8577, Japan 3 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 4 PREST, JST, Saitama 332-0012, Japan 5 WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 6 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan ABSTRACT In the previous work, it is reported that the Spin-Seebeck effect (SSE), which refer to the generation of a spin current from a temperature gradient, can be enhanced by Fe interface treatment. Here, we investigated the Fe thickness (dFe) dependency of spin-Seebeck voltage (VSSE) and mixing conductance (gr) in Pt/Fe/Bi:YIG/SGGG system. As a result, magnitude of VSSE had a peak at dFe ҹ 1 ML (monolayer , ҹ0.3 mm), and also increase of gr was saturated at this point. It suggests that VSSE increase with increasing gr when dFe is smaller than 1.0 ML. For the case in which dFe is larger than 1.0ML, however, VSSE decreases due to a spin current decay in Fe layer with a constant gr. These experimental results are consistent with previous theoretical works. INTRODUCTION In various places such as automobiles, factories and buildings, there is enormous thermal energy wasted. In order to reuse this thermal energy, thermoelectric devices based on the Seebeck effect have been studied for a long time [1]. In recent years, another category of thermoelectric devices based on the spin-Seebeck effect (SSE) [2-10] have been closely watched. They are called spin-Seebeck devices [11]. This device has a potential of reducing a manufacturing cost compare to the conventional thermoelectric devices. Its simple bilayer structure with a ferromagnetic insulator (FI) layer and a paramagnetic metallic (PM) layer provides us various easy fabrication methods such as a coating [11]. In the spin Seebeck device, a spin-current Js is generated in FI from a temperature gradient T by the SSE. In PM, the spin-current injected from FI is converted into an electric current Jc by the Invers-spin-Hall effect (ISHE) [12-16]. In this way, the spin-Seebeck device generates the electric current from the temperature gradient via the spin-current. Spin-Seebeck-driven thermoelectric voltage VSSE can be described as a following expression
VSSE v T SH J s v T SH g r
(1)
where, θSH is the spin Hall angle that corresponds to a conversion efficiency from the spincurrent into electric-current by the ISHE, and gr is the mixing conductance standing for the efficiency of spin-current pumping from FI into PM.
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