posted on 2021-03-16, 20:09authored byDmitriy Ksenzov, Alexei A. Maznev, Vivek Unikandanunni, Filippo Bencivenga, Flavio Capotondi, Antonio Caretta, Laura Foglia, Marco Malvestuto, Claudio Masciovecchio, Riccardo Mincigrucci, Keith A. Nelson, Matteo Pancaldi, Emanuele Pedersoli, Lisa Randolph, Hendrik Rahmann, Sergei Urazhdin, Stefano Bonetti, Christian Gutt
We
utilize coherent femtosecond extreme ultraviolet (EUV) pulses
from a free electron laser (FEL) to generate transient periodic magnetization
patterns with periods as short as 44 nm. Combining spatially periodic
excitation with resonant probing at the M-edge of cobalt allows us
to create and probe transient gratings of electronic and magnetic
excitations in a CoGd alloy. In a demagnetized sample, we observe
an electronic excitation with a rise time close to the FEL pulse duration
and ∼0.5 ps decay time indicative of electron–phonon
relaxation. When the sample is magnetized to saturation in an external
field, we observe a magnetization grating, which appears on a subpicosecond
time scale as the sample is demagnetized at the maxima of the EUV
intensity and then decays on the time scale of tens of picoseconds
via thermal diffusion. The described approach opens multiple avenues
for studying dynamics of ultrafast magnetic phenomena on nanometer
length scales.