Ultrafast dynamics of spin waves and coercivity of a FePt/FeNi exchange coupling film studied by femtosecond laser Kerr spectroscopy

Shufa Li; Zhifeng Chen; Chuyuan Cheng; Jiaming Li; Shiming Zhou; Tianshu Lai

doi:10.1117/12.2016670

24 January 2013 Ultrafast dynamics of spin waves and coercivity of a FePt/FeNi exchange coupling film studied by femtosecond laser Kerr spectroscopy

Shufa Li, Zhifeng Chen, Chuyuan Cheng, Jiaming Li, Shiming Zhou, Tianshu Lai

Author Affiliations +

Proceedings Volume 8782, 2012 International Workshop on Information Storage and Ninth International Symposium on Optical Storage; 87820Q (2013) https://doi.org/10.1117/12.2016670
Event: 2012 International Workshop on Information Data Storage and Ninth International Symposium on Optical Storage, 2012, Shanghai, China

Abstract

Ultrafast dynamics of spin waves and coercivity of a FePt/FeNi exchange coupling film is studied by femtosecond laser Kerr spectroscopy. Magnetization-precession spin waves are observed. Time-delayed magneto-optical Kerr hysteresis loop (TDMOKHL) technique is used to study the dynamics of coercivity of the magnetic film under laser excitations as done usually. However, we find that the dynamics of coercivity revealed by TDMOKHL technique does not reflect the evolution of initial coercivity given by the initial hysteresis loop with no pump excitation, but does that of final coercivity under laser excitation. The final coercivity is given by the hysteresis loop measured at a negative pump-probe delay time under pump excitation. The evolution of initial coercivity can be observed only under a weak pump excitation in which magnetic system behaves reversible magnetically. In general, TDMOKHL technique can not track the evolution of coercivity of a magnetic system because TDMOKHLs do not reflect the time evolution of initial hysteresis loop with no laser excitation. The correctness of all previous reports on the dynamics of coercivity and magnetic-order transition of a laser-excited magnetic system needs reexamining if those reports were dependent on TDMOKHL technique. The oscillatory recovery behavior of final coercivity is observed under pump excitation and ascribed to metastability of zero magnetization state.

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Shufa Li, Zhifeng Chen, Chuyuan Cheng, Jiaming Li, Shiming Zhou, and Tianshu Lai "Ultrafast dynamics of spin waves and coercivity of a FePt/FeNi exchange coupling film studied by femtosecond laser Kerr spectroscopy", Proc. SPIE 8782, 2012 International Workshop on Information Storage and Ninth International Symposium on Optical Storage, 87820Q (24 January 2013); https://doi.org/10.1117/12.2016670

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KEYWORDS

Magnetism

Femtosecond phenomena

Picosecond phenomena

Ultrafast laser spectroscopy

Spectroscopy

Laser systems engineering

Switching

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