Spin-Transfer-Torques at a Ferromagnet/Antiferromagnet Interface*

Spintronics in ferromagnetic systems is built on a complementary set of phenomena in which the magnetic configuration of the system influences its transport properties and vice versa. Giant magnetoresistance (GMR) [1] and spin- transfer-torque (STT) [2] phenomena are typical examples of such interconnections. Recently, MacDonald and co-workers [3] predicted that corresponding effects ought to occur in systems where ferromagnetic (F) components are replaced by antiferromagnets (AFM). I will present our experimental search for these new AFM effects which may potentially lead to a new all-antiferromagnetic spintronics where antiferromagnets are used in place of ferromagnets. In particular I will focus on our experiments with exchange-biased spin valves [4] where extreme current densities were found to affect the exchange bias at F/AFM interface [5-7]. As exchange bias is known to be associated with interfacial AFM magnetic moments, our observation can be taken as the first evidence of STT effect in AFM materials. \\[4pt] [1] M. N. Baibich et al., Phys. Rev. Lett. 61, 2472 (1988); G. Binasch et al., Phys. Rev. B 39, 4828 (1989). \\[0pt] [2] J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1 (1996); L. Berger, J. Appl. Phys. 81, 4880 (1997); M. Tsoi et al., Phys. Rev. Lett. 80, 4281 (1998). \\[0pt] [3] A. S. N\'u\~nez et al., Phys. Rev. B 73, 214426 (2006); \\[0pt] [4] Z. Wei et al., Phys. Rev. Lett. 98, 116603 (2007). \\[0pt] [5] S. Urazhdin and N. Anthony, Phys. Rev. Lett. 99, 046602 (2007). \\[0pt] [6] X-L.Tang et al., Appl. Phys. Lett. 91, 122504 (2007). \\[0pt] [7] N. V. Dai et al., Phys. Rev. B77, 132406 (2008).