In order to follow the evolution of the
magnetization in an applied magnetic
field, we recorded scattering patterns
of the magnetic configurations, making
use of the x-ray magnetic circular
dichroism (XMCD) at the Fe L
3
edge [5].
By calculating the difference between
scattering patterns recorded with right
and left circularly polarized x-rays, we
observed a stepwise change of the XMCD
contrast. An example of a dichroic pattern
is shown in Figure
➌
a
for a value
of the applied magnetic field close
to the coercive field.
Artificial square ice is composed
of nanomagnets with two orientations,
forming two distinct sublattices orthogonal
to each other, which scatter the photons
with different angular dependence.
Therefore the dichroic patterns contain
information not only on the total
magnetization of the array, but also
on the contributions from
the individual sublattices. To extract these
contributions, we numerically simulated
the scattering patterns taking into account
the magnetization for each sublattice.
Fitting the model to the experiment,
we could quantitatively reproduce
the dichroic intensity up to the second
order Bragg peaks (Figure
➌
b
), and
therefore estimate the number of reversed
moments in each sublattice for a given
applied field.
In this work, we have demonstrated
that important insights into the magnetic
configuration of artificial spin ice can
be obtained by SXRMS. This study opens
the way to more sophisticated
experiments, such as scattering with
coherent x-rays, which will play
an important role in the further
investigation of thermally active systems
and the understanding of frustration
in systems with competing interactions.
Magnetization reversal in individual sublattices
SEXTANTS beamline
ASSOCIATED PUBLICATION
Extended reciprocal space observation
of artificial spin ice with x-ray resonant
magnetic scattering
J. Perron, L. Anghinolfi*, B. Tudu, N. Jaouen,
J.M. Tonnerre, M. Sacchi, F. Nolting, J. Lüning
and L.J. Heyderman
Physical Review B 88 (2013), 214424
*Laboratory for Mesoscopic Systems,
Department of Materials, ETH Zürich, 8093
Zürich, Switzerland; Paul Scherrer Institut,
5232 Villigen PSI, Switzerland
CORRESPONDING AUTHOR
➋
Scattering pattern measured
on the as-grown artificial
square ice at the Fe L
3
edge.
The structural Bragg peaks
are coloured in black, and the
magnetic peaks in red. The
dashed frame highlights the
first order diffraction peaks.
➌
(
a
) Dichroic scattering pattern measured at the Fe L
3
edge at the coercive field. (
b
) Numerical simulation
of the scattering pattern. By matching the Bragg peak intensities, we are able to determine the number
of reversed nanomagnets in each sublattice. The black dashed frames are a guide to the eyes.
REFERENCES
[1] L.J. Heyderman and R.L. Stamps. J. Phys.:
Condens. Matter. 25 (2013), 363201
[2] R.F. Wang et al. Nature 439 (2006), 303
[3] A. Farhan et al. Nat. Phys. 9 (2013), 375
[4] J.P Morgan et al. Nat. Phys. 7 (2011), 75
[5] C.T. Chen et al. Phys. Rev. B 42 (1990),
7262(R)
107
SOLEIL
HIGHLIGHTS
2013
