[phas-dept] Apr. 13 (Thursday) 4 PM - Physics and Astronomy Colloquium

[Heungman Park]

Spring 2017 Colloquium

Department of Physics & Astronomy

April 13, Thursday, 4-5 PM in Science Building 127

(coffee and cookies will be served at 3:50 PM)

Spinstronics

>From Ferromagnets To Antiferromagnets
Dr. Maxim Tsoi

University of Texas at Austin

[https://lh3.googleusercontent.com/niqhd2u-fGXWkyZiYCgMG5PWcyr0-5YFLcTeCc5t4IuTVP0MJWWO6bxPAeVTl1dqcFhgAwFVZQL75pyHUKcEPh2cymvP4BvRJ3trjn_E_0BKlw_7j99QYmbIJF0qyz0FmaJg8gko]

Dr. Maxim Tsoi is a Professor of Physics at the University of Texas at Austin.  A graduate of Moscow Institute of Physics and Technology, Russia (B.S. 1993; M.S. 1995) and Konstanz University, Germany (Ph.D. 1998), Dr. Tsoi joined the UT faculty in 2003, after serving as a postdoctoral member of the technical staff at IBM Almaden Research Center, Michigan State University, and the Grenoble High Magnetic Field Laborotory of Max-Planck-Institut für Festkörperforschung and Centre National de la Recherche Scientifique. His research interests include conduction electron/interface interactions, spin-polarized transport in mesoscopic structures, nanomagnetism and spintronics. Dr. Tsoi is a pioneer of experimental studies of Spin-Transfer Torque (STT). He was the first to demonstrate STT phenomenon in experiments with magnetic multilayers [1].  His point-contact experiments with microwaves provided the first evidence of STT nano-oscillators [2]. His experiments with exchange-biased spin valves [3] gave the first evidence of STT in antiferromagnetic (AFM) materials and can be taken as the first step towards all-AFM spintronics.  Dr. Tsoi is a recipient of the “Ragnar Holm Plaquette” awarded by the Royal Institute of Technology, Stockholm, Sweden (2002) and the National Science Foundation CAREER Award (2006). More information about Dr. Tsoi and his research can be found at

https://web2.ph.utexas.edu/~tsoi/

[1]. M. Tsoi, A. G. M. Jansen, J. Bass, W.-C. Chiang, M. Seck, V. Tsoi, and P. Wyder, «Excitation of a magnetic multilayer by an electric current», Phys. Rev. Lett. 80, 4281-4284 (1998).

[2]. M. Tsoi, A. G. M. Jansen, J. Bass, W.-C. Chiang, V. Tsoi, and P. Wyder, «Generation and detection of phase-coherent current-driven magnons in magnetic multilayers», Nature 406, 46-48 (2000).

[3]. Z. Wei, A. Sharma, A. S. Nunez, P. M. Haney, R. A. Duine, J. Bass, A. H. MacDonald, and M. Tsoi, «Changing exchange bias in spin valves with an electric current», Phys. Rev. Lett. 98, 116603 (2007).



Abstract: Spintronics is a new technological discipline which refers to studying the role played by an electron spin in solid state physics and aims at developing a revolutionary new class of electronic devices based on the spin degree of freedom of the electron in addition to, or in place of, the charge. Spintronics is built on a complementary set of phenomena in which the magnetic configuration of a system influences its transport properties and vice versa. In ferromagnetic systems these interconnections are exemplified by Giant Magnetoresistance (GMR) – where the system’s resistance depends on the relative orientation of magnetic moments in constituent ferromagnetic parts [1], and Spin Transfer Torque (STT) – in which an electrical current can perturb the system’s magnetic state [2].  Such transport phenomena provide a means to read and write information in magnetic memory devices like STTRAM. Similar interconnections were proposed [3] to occur in systems where ferromagnetic components are replaced with antiferromagnets, thus leading to a new field of research – antiferromagnetic (AFM) spintronics – where unique properties of AFM materials are exploited to achieve new and improved device functionalities.  AFMs are especially interesting for high-speed memory applications thanks to their high natural frequencies.

Recently, we demonstrated experimentally the existence of such interconnections in antiferromagnetic Mott insulators Sr2IrO4 and Sr3Ir2O7: (i) we found a very large anisotropic magnetoresistance (AMR) which can be used to monitor (read) the magnetic state of AFM [4]; (ii) we demonstrated the feasibility of reversible resistive switching driven by high-density currents/high electric fields [5] which can be used for writing in AFM memory applications; (iii) we observed for the first time an effect of gigahertz radiation on transport properties of an antiferromagnet without any involvement of ferromagnets [6]. These results support the feasibility of AFM spintronics where antiferromagnets are used in place of ferromagnets.

This work was supported in part by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA, by NSF grant DMR-1207577, and by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2015-CRG4-2626.

[1] M. N. Baibich et al., Phys. Rev. Lett. 61, 2472 (1988); G. Binasch et al., Phys. Rev. B 39, 4828 (1989); [2] J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996); L. Berger, Phys. Rev. B 54, 9353 (1996); M. Tsoi et al., Phys. Rev. Lett. 80, 4281 (1998)

[3] A. S. Núñez et al., Phys. Rev. B 73, 214426 (2006); A. H. MacDonald, M. Tsoi, Phil. Trans. R. Soc. A 369, 3098 (2011)

[4] C. Wang et al., Phys. Rev. X 4, 041034 (2014)

[5] C. Wang et al., Phys. Rev. B 92, 115136 (2015)

[6] H. Seinige et al., Phys. Rev. B 94, 214434 (2016).

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