Affiliation:
1. TU Wien
2. Institut National de la Recherche Scientifique
3. Universität Hamburg
4. Paul Scherrer Institute
5. few-cycle, Inc.
6. Université de Genève
7. Université de Lorraine
8. Sorbonne Université
9. Synchrotron SOLEIL
10. Deutsches Elektronen-Synchrotron DESY
11. Fudan University
Abstract
Development of ultrafast table-top x-ray sources that can map various
spin, orbital, and electronic configurations and reordering processes
on their natural time and length scales is an essential topic for
modern condensed matter physics as well as ultrafast science. In this
work, we demonstrate spatiotemporally resolved resonant magnetic
scattering (XRMS) to probe the inner-shell 4d electrons of a
rare-earth (RE) composite ferrimagnetic system using a bright
>
200
e
V
soft x-ray high harmonic generation
(HHG) source, which is relevant for future energy-efficient,
high-speed spintronic applications. The XRMS is enabled by direct
driving of the HHG process with power-scalable, high-energy Yb laser
technology. The optimally phase-matched broadband plateau of the HHG
offers a record photon flux (
>
2
×
1
0
9
p
h
o
t
o
n
s
/
s
/
1
%
bandwidth) with excellent spatial
coherence and covers the entire resonant energy range of RE’s
N
4
,
5
edges. We verify the underlying
physics of our x-ray generation strategy through the analysis of
microscopic and macroscopic processes. Using a CoTb alloy as a
prototypical ferrimagnetic system, we retrieve the spin dynamics, and
resolve a fast demagnetization time of
500
±
126
f
s
, concomitant with an expansion of the
domain periodicity, corresponding to a domain wall velocity of
∼
750
m
/
s
. The results confirm that, far from
cross-contamination of low-energy absorption edges in multi-element
systems, the highly localized states of
4
d
electrons associated with the
N
4
,
5
edges can provide high-quality
core-level magnetic information on par with what can be obtained at
the
M
edges, which is currently accessible
only at large-scale x-ray facilities. The analysis also indicates the
rich material-, composition-, and probing-energy-dependent driving
mechanism of RE-associated multicomponent systems. Considering the
rapid emergence of high-power Yb lasers combined with novel nonlinear
compression technology, this work indicates potential for
next-generation high-performance soft x-ray HHG-based sources in
future extremely photon-hungry applications on the table-top scale,
such as probing electronic motion in biologically relevant molecules
in their physiological environment (liquid phase), and advanced
coherent imaging of nano-engineered devices with
5
∼
8
n
m
resolution.
Funder
Deutsche
Forschungsgemeinschaft
Fonds de recherche du Québec – Nature et
technologies
Natural Sciences and Engineering Research
Council of Canada
Shanghai Municipal Science and Technology
Basic Research
National Key Research and Development
Program of China
National Natural Science Foundation of
China
Institut national des sciences de
l’Univers
Agence Nationale de la
Recherche
Austrian Science Fund
Marie Sklodowska-Curie
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials
Cited by
8 articles.
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