Femtosecond modification of electron localization and transfer of angular momentum in nickel

C. Stamm, T. Kachel, N. Pontius, R. Mitzner, T. Quast, K. Holldack, S. Khan, C. Lupulescu, E. F. Aziz, M. Wietstruk, H. A. Dürr, W. Eberhardt

Research output: Contribution to journalArticlepeer-review

464 Scopus citations

Abstract

The rapidly increasing information density required of modern magnetic data storage devices raises the question of the fundamental limits in bit size and writing speed. At present, the magnetization reversal of a bit can occur as quickly as 200ps (ref.1). A fundamental limit has been explored by using intense magnetic-field pulses of 2ps duration leading to a non-deterministic magnetization reversal. For this process, dissipation of spin angular momentum to other degrees of freedom on an ultrafast timescale is crucial. An even faster regime down to 100fs or below might be reached by non-thermal control of magnetization with femtosecond laser radiation. Here, we show that an efficient novel channel for angular momentum dissipation to the lattice can be opened by femtosecond laser excitation of a ferromagnet. For the first time, the quenching of spin angular momentum and its transfer to the lattice with a time constant of 120±70fs is determined unambiguously with X-ray magnetic circular dichroism. We report the first femtosecond time-resolved X-ray absorption spectroscopy data over an entire absorption edge, which are consistent with an unexpected increase in valence-electron localization during the first 120±50fs, possibly providing the driving force behind femtosecond spin-lattice relaxation.

Original languageEnglish
Pages (from-to)740-743
Number of pages4
JournalNature Materials
Volume6
Issue number10
DOIs
StatePublished - Oct 2007
Externally publishedYes

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