Since the seminal discovery of giant magnetoresistance in magnetic multilayers and tunneling magnetoresistance in magnetic tunnel junctions, the exploration of spin-dependent electronic transport has provided a promising avenue for applications in data storage and processing.1 Devices based on the electron spin typically require the application of magnetic fields or spin torques generated by large currents, consuming power and producing heat, hence limiting the application of such devices. To avoid the need for large currents, there have been recent efforts toward manipulating magnetization by the application of electric fields.2 Such magnetoelectric effects can be induced at the surfaces and interfaces of ferromagnetic metals affecting both the interface magnetization and the interface magnetocrystalline anisotropy.3,4 Ferroelectric materials are especially helpful in this regard because they possess a spontaneous electrical polarization which, when reversed by an electric field, can induce a large magnetoelectric response at the interface with a magnetic metal.5 Importantly, ferroelectric films can now be made thin enough to allow measurable electron tunneling while maintaining a stable and switchable polarization.6-8 Modeling and experiments show that ferroelectric tunnel junctions allow producing giant resistive-switching effects and the control of spin-polarization of the tunneling current.9,10 This talk will overview our recent research efforts and discuss underlying physical principles associated with magnetoelectric interfaces and the effect of ferroelectricity on electron and spin transport.
1. E. Y. Tsymbal and I. Žutić, Eds., Handbook of Spin Transport and Magnetism (CRC press, Boca Raton, FL, 2011), 808 pp.
2. J. P. Velev, S. S. Jaswal, and E. Y. Tsymbal, “Multiferroic and magnetoelectric materials and interfaces,”Philosophical Transactions of the Royal Society A 369, 3069 (2011).
3. C.-G. Duan, J. P. Velev, R. F. Sabirianov, Z. Zhu, J. Chu, S. S. Jaswal, and E. Y. Tsymbal, “Surface magnetoelectric effect in ferromagnetic metal films,” Physical Review Letters 101, 137201 (2008).
4. E. Y. Tsymbal, “Spintronics: Electric toggling of magnets,” Nature Materials 11, 12 (2012).
5. J. D. Burton and E. Y. Tsymbal, “Prediction of electrically-induced magnetic reconstruction at the manganite/ferroelectric interface,” Physical Review B 80, 174406 (2009).
6. E. Y. Tsymbal and H. Kohlstedt, “Tunneling across a ferroelectric,” Science 313, 181 (2006).
7. E. Y. Tsymbal, A. Gruverman, V. Garcia, M. Bibes, and A. Barthélémy, “Ferroelectric and multiferroic tunnel junctions,” MRS Bulletin 37, 138 (2012).
8. E. Y. Tsymbal and A. Gruverman, “Ferroelectric tunnel junctions: Beyond the barrier,” Nature Materials 12, 602 (2013).
9. J. D. Burton and E. Y. Tsymbal, “A giant tunneling electroresistance effect driven by electrically controlled spin valve at a complex oxide interface,” Physical Review Letters 106, 157203 (2011).
10. Y. W. Yin, J. D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, A. Gruverman, X. G. Li, E. Y. Tsymbal, and Q. Li, “Enhanced tunnelling electroresistance effect due to a ferroelectrically induced phase transition at a magnetic complex oxide interface,” Nature Materials 12, 397 (2013).
Argonne Physics Division Colloquium Schedule