The manipulation of magnetic materials without the use of magnetic fields is of great fundamental and technical interest. The discovery of spin-transfer torque (STT) [1,2] allowed us to control the magnetization direction electrically in magnetic devices within nanoseconds, which paved the way for non-volatile applications such as spin-transfer-torque magnetoresistive random access memory (STT-MRAM). However, current-induced STT switching below a few hundred picoseconds with low power consumption while maintaining high thermal stability is challenging. Ultra-short optical pulses can induce spin angular momentum transfer in a ferromagnetic spin valve, resulting in different demagnetization time depending on its magnetic configuration within less than a picosecond [3]. However, magnetization reversal in ferromagnetic spin valves by a single femtosecond laser pulse has not been achieved. In this seminar, I will show our recent work, where we demonstrated sub- picosecond magnetization reversal of a Co/Pt ferromagnetic layer induced by a single femtosecond laser pulse within a common [Co/Pt]/Cu/[Co/Pt] perpendicular spin-valve structure [4, 5]
References :
[1] J. C. Slonczewski, Journal of Magnetism and Magnetic Materials 159, L1‒L7 (1996).
[2] L. Berger, Phys. Rev. B 54, 9353‒9358 (1996).
[3] G. Malinowski et al ., Nature Phys., 4, 855-858 (2008).
[4] S. Mangin et al., Nature Mater 5, 210‒215 (2006)
[5] J. Igarashi et al., under review.

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