Large pure spin current generation in metallic nanostructures
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I N V I T E D PA P E R
Large pure spin current generation in metallic nanostructures Saidur R. Bakaul · Shaojie Hu · Takashi Kimura
Received: 2 September 2012 / Accepted: 8 December 2012 / Published online: 19 December 2012 © Springer-Verlag Berlin Heidelberg 2012
Abstract Pure spin current corresponds to the flow of spin angular momentum without associating any net charge current, and possesses potential to be incorporated in special functional and high-performance devices based on nonlocal spin injection. To utilize pure spin current in practical devices, it is imperative to increase the spin generation efficiency. In this article we discuss two special configurations of nonlocal devices, known as multi-terminal injector and nanopillar devices, which possess immense potential to overcome the Joule heating problem, the key bottleneck to enhance the pure spin current generation. We also demonstrate magnetization switching of a nanosized ferromagnet due to pure spin current injection in a nanopillar-based nonlocal device.
1 Introduction Ferromagnetic (F)/nonmagnetic (N) metal hybrid nanostructures show intriguing transport properties in association with spin-exchange and spin–orbit interactions [1, 2]. NanoelecS.R. Bakaul · S. Hu · T. Kimura () Advanced Electronics Research Division, INAMORI Frontier Research Center, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan e-mail: [email protected] S. Hu Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan T. Kimura CREST, Japan Science and Technology Agency, Sanbancho, Tokyo 102-0075, Japan
tronic devices utilizing such spin-transport properties have great advantages over conventional electronic devices because of the additional spin functionalities with their nonvolatile properties [3]. In the spin-dependent transports, spin current, flow of the spin angular momentum, is the key ingredient [4]. Therefore, establishing the manipulation of the spin current is indispensable for utilizing the spin transport efficiently in nano spintronic devices, as well as for further understanding the basic physics of the spin transports. In order to investigate the spin current, up to now most experiments performed by other groups have been carried out in a vertical structure called the current perpendicular to plane (CPP) configuration [5, 6]. It is, however, difficult to fabricate multi-terminal devices with vertical structures, so one can obtain only limited information about the series resistance of the magnetic multi-layers. On the contrary, laterally configured F/N hybrid nanostructures have great advantages for developing the multi-terminal spintronic devices because they allow a flexible probe configuration [7, 8]. Especially, pure spin current created by nonlocal spin injection in the lateral structures is a powerful tool for detecting the electric signals purely related to the spin transports [9–13] as, in this case, the charge current induced spurious signals such as anisotropic magnetoresi
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