Voltage tuning of thermal spin current in ferromagnetic tunnel contacts to semiconductors.
Spin currents are paramount to manipulate the magnetization of ferromagnetic elements in spin-based memory, logic and microwave devices, and to induce spin polarization in non-magnetic materials. A unique approach to create spin currents employs thermal gradients and heat flow. Here we demonstrate that a thermal spin current can be tuned conveniently by a voltage. In magnetic tunnel contacts to semiconductors (silicon and germanium), it is shown that a modest voltage (~200 mV) changes the thermal spin current induced by Seebeck spin tunnelling by a factor of five, because it modifies the relevant tunnelling states and thereby the spin-dependent thermoelectric parameters. The magnitude and direction of the spin current is also modulated by combining electrical and thermal spin currents with equal or opposite sign. The results demonstrate that spin-dependent thermoelectric properties away from the Fermi energy are accessible, and open the way towards tailoring thermal spin currents and torques by voltage, rather than material design.
National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Kun-Rok
KR
Jeon
Center for Spintronics Research, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea.
Byoung-Chul
BC
Min
National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Aurelie
A
Spiesser
National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Hidekazu
H
Saito
1] Department of Physics and Center for Nanospinics of Spintronic Materials, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea [2] Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Korea.
Sung-Chul
SC
Shin
National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Shinji
S
Yuasa
National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Ron
R
Jansen