Effective field measurements and spin torque dynamics in magnetic nanostuctures

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• The Sir martin Wood Lecture Prize - Dr Masamitsu Hayashi, National Institute of Materials Science, Tsukuba, Japan
• Wednesday 10 June 2015, 14:00-15:00
• Small Lecture Theatre (Bragg Building), Cavendish Laboratory.

If you have a question about this talk, please contact Linda Whyles.

Followed by refreshments

Strong spin-orbit effects in magnetic heterostructures with broken structural inversion symmetry have opened new paradigms to control magnetic moments electrically[1, 2]. An ultrathin magnetic layer sandwiched between a heavy metal layer and an insulating oxide layer form the base of inversion symmetry broken magnetic heterostructures. In such structures, extremely small current applied along the film plane can trigger magnetization switching and domain wall motion[3, 4]. Key to the power efficient magnetization control is the large spin-orbit coupling of the heterostructure. The strong spin orbit coupling constant of the heavy metal layer enables generation of large spin current that can impinge upon the magnetic layer to exert torque on the magnetic moments, now commonly referred to as the spin-orbit torque. At interfaces, spin orbit coupling can cause the ultrathin magnetic layer to form a chiral magnetic structure, via the Dzyaloshinskii-Moriya interaction, that can be manipulated by the spin current. We have studied the characteristics of spin-orbit torques in ultrathin magnetic heterostructures with magnetization oriented perpendicular to the film plane5. The layer thickness and temperature dependence of the torque are analyzed to illustrate the importance of unusual spin transmission at the interface of heavy metal and magnetic layers[6, 7]. Current induced domain nucleation and domain wall motion in related structures will be discussed in connection with the chiral magnetic texture8 developed in magnetic heterostructures. [1] I. M. Miron et al., Nature 476, 189 (2011). [2] L. Liu et al., Science 336, 555 (2012). [3] S. S. P. Parkin et al., Science 320, 190 (2008). [4] M. Hayashi et al., Science 320, 209 (2008). [5] J. Sinha et al., Appl. Phys. Lett. 102 242405 (2013). [6] J. Kim et al., Nat. Mater. 12, 240 (2013). [7] J. Kim et al., Phys. Rev. B 89 , 174424 (2014). [8] J. Torrejon et al., Nature Comm. 5, 4655 (2014).

Dr Hayashi was awarded the Sir Martin Wood Prize at the Millennium Science Forum which took place at the British Embassy, Tokyo, November 2014. The Millennium Science Forum was established in 1998 to promote scientific exchange between Britain and Japan and recognise the work of outstanding young Japanese researchers. The prize is named after Sir Martin Wood, Founder of Oxford Instruments.

This talk is part of the Thin Film Magnetism Group Seminars series.

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