[20a-D104-1~11] 10.4 半導体スピントロニクス・超伝導・強相関

▲ [20a-D104-9] Magneto-thermopower in Ferromagnetic Semiconductor In_1-xFe_xSb

〇(P)CONG TINH BUI¹、CHRISTINA GARCIA²、NGUYEN THANH TU³、MASAAKI TANAKA³、PHAM NAM HAI^1,3 (1.Tokyo Tech.、2.UCSB、3.Univ. of Tokyo)

キーワード：ferromagnetic semiconductor, magneto-thermopower, planar Nernst effect

Spin caloritronics, which studies the interaction of spin current with heat current, has recently attracted much attention due to its novel physical effects and possible applications to thermoelectric as well as spintronic devices. Among promising candidates for spin caloritronics, ferromagnetic semiconductors (FMS) are technologically interesting as they possess both ferromagnetic and semiconducting properties which could be exploited for development of more efficient energy harvesting devices. In this research, we systematically studied the transverse magneto-thermoelectric effects in an n-type In_1-xFe_xSb (x = 16%) thin film [1], epitaxially grown on GaAs (001) substrates by molecular beam epitaxy. The sample exhibits semiconducting and ferromagnetic behavior based on resistivity, magnetization, anomalous Hall effect, and magnetic circular dichroism measurements, which show the Curie temperature of 127 K. The transverse thermal voltage V_xy increases linearly with the temperature gradient, indicating the thermoelectric origin of the effect. We find that the transverse Seebeck coefficient S_xy increases monotonically at high magnetic fields, and also increases with increasing temperature up to T_C. This might be related to the negative magnetoresistance ρ_xx at high magnetic fields following the Mott relation S_xy ~ 1/ρ_xx [2]. Meanwhile, in a low magnetic field range, the polarity of S_xy depends on the angle α between the external magnetic field and the temperature gradient. Furthermore, α-dependence of S_xy at 5 K and 100 K under a magnetic field of 8 kG follows the sin(2α) function, indicating the planar Nernst effect (PNE) origin of S_xy at low fields. However, PNE is nearly temperature independent (~ 0.3 μV/K), despite the large change in the conductivity at 5 K and 100 K. Our findings are the first step toward better understanding of the magneto-thermoelectric phenomena in similar Fe-doped ferromagnetic semiconductors.

Refs. [1] N. T. Tu et al., arXiv:1706.00735. [2] Y. Pu et al., Phys. Rev. Lett. 101, 117208 (2008).