Laser-induced ultrafast demagnetization in the presence of a nanoscale magnetic domain network.

Vodungbo, Boris; Gautier, Julien; Lambert, Guillaume; Sardinha, Anna Barszczak; Lozano, Magali; Sebban, Stéphane; Ducousso, Mathieu; Boutu, Willem et al. · Nat Commun · 2012

basic_science · Level V

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Abstract

Femtosecond magnetization phenomena have been challenging our understanding for over a decade. Most experiments have relied on infrared femtosecond lasers, limiting the spatial resolution to a few micrometres. With the advent of femtosecond X-ray sources, nanometric resolution can now be reached, which matches key length scales in femtomagnetism such as the travelling length of excited 'hot' electrons on a femtosecond timescale. Here we study laser-induced ultrafast demagnetization in [Co/Pd](30) multilayer films, which, for the first time, achieves a spatial resolution better than 100 nm by using femtosecond soft X-ray pulses. This allows us to follow the femtosecond demagnetization process in a magnetic system consisting of alternating nanometric domains of opposite magnetization. No modification of the magnetic structure is observed, but, in comparison with uniformly magnetized systems of similar composition, we find a significantly faster demagnetization time. We argue that this may be caused by direct transfer of spin angular momentum between neighbouring domains.