Evidence for thermal mechanisms in laser-induced femtosecond spin dynamics

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Output type: Journal article

Author list: Atxitia U, Chubykalo-Fesenko O, Walowski J, Mann A, Munzenberg M

Publisher: American Physical Society

Publication year: 2010

Journal: Physical review B (1098-0121)

Volume number: 81

Issue number: 17

ISSN: 1098-0121

eISSN: 1550-235X

Languages: English-Great Britain (EN-GB)

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Open access status: closed

Abstract

Recent pump-probe experiments using powerful femtosecond lasers and x-ray magnetic circular dichroism have opened a debate on the origin of the magnetization modification on the femtosecond time scale. We show a quantitative agreement between femtosecond optical pump-probe experiments and thermal micromagnetic modeling in nickel, which reveals a predominant thermal demagnetization mechanism. Magnetic fluctuations are introduced in the system as spin-flip processes due to scattering mechanisms in the electron system. In our model the Landau-Lifshitz-Bloch equation for a macrospin (containing the statistically averaged magnetic fluctuations) is coupled to the electronic temperature of the two-temperature model whose parameters are extracted from the measured reflectivity. We show that the demagnetization and the magnetization recovery time slow down as the laser pump fluence is increased and identify the longitudinal relaxation as a key factor for the observed behavior.

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