ferrofluids, photomagnetic systems
properties of magnetic nanosized objects:
of soft and hard x-ray
- Development of
RIXS-MCD with hard x-rays, a novel (photon-in, photon out) magnetic spectroscopy
Experimental methods : core
level spectroscopies on synchrotron radiation facilities (mainly ESRF
- X-ray Absorption Spectroscopy
(XANES, EXAFS) in situ
- X-ray Emission
Inelastic X-ray Scattering (RIXS)
Spectroscopies: XMCD (X-ray Magnetic Circular Dichroism) and RIXS-MCD
methods : modeling of core level spectroscopies and dichroisms (XAS,
RIXS, XMCD, XNLD, XNCD)
- Single particle calculations (DFT,
DFT+U) : QUANTUM-ESPRESSO,
- Multielectronic calculations (Ligand
Field Multiplet Theory): Quanty, CTM4XAS, TT MULTIPLETS
- Tensor analysis of
Principle of RIXS-MCD
is a newly developed spectroscopy that combines photon-in,
photon-out Resonant Inelastic X-ray Scattering (RIXS)
with X-ray Magnetic Circular Dichroism (XMCD).
When performed at the K pre-edge
of 3d elements (1s2 2p6
3dN --> 1s1 2p6
3dN+1 --> 1s2 2p5
3dN+1), it exploits the advantages of hard
x-rays (i.e., bulk sensitivity, low
with the high resolution of RIXS.
shown that hard x-ray RIXS-MCD can be a valuable alternative to soft
XMCD, when using demanding sample environments, such as liquid
when investigating materials whose surface may not be representative of
Additionally, the 2D character (photon-in, photon-out) of RIXS-MCD enables to
the spectroscopic signatures of different valences.
The figure below illustrates the
principle of a RIXS-MCD experiment (left), and the RIXS and
RIXS-MCD planes measured at the Fe K edge in magnetite.
K-edge XMCD effect
in magnetite using photon in - photon out spectroscopy.
Applications of RIXS-MCD
RIXS-MCD can be applied
in a quantitative way to investigate systems for which the use of soft
is rather challenging, such as 15 nm-thick magnetic layers buried under
nm Au / Pt, for which element- and site- selective hysteresis loops
Sikora, A. Juhin,
G. Simon, M. Zaj.c, K. Biernacka, Cz. Kapusta, L. Morellon, M. R.
P. Glatzel, Journal of Applied Physics, 111, 07E301(2012).
Bimagnetic core-shell nanoparticles
core-shell nanoparticles currently focus high interest owing to
their applications in the fields of biomedicine (hyperthermia, highly
biosensors, improved MRI...) and technology (magnetic recording,
magnets…). The fine tailoring of particles requires a deep
knowledge of their
internal structure and morphology, from which the properties are directly
inherited. In nominally γ-Fe2O3/Mn3O4
is the smoking gun evidence for the existence of a magnetic
(Mn,Fe) spinel growing from the core γ-Fe2O3
and the shell Mn3O4. Combined
with TEM-EELS experiments, a quantitative multilayered
structure is proposed (Figure below), which allows understanding the
the interface quality on the measured magnetic properties.
A. Juhin, A.
López-Ortega, M. Sikora, C. Carvallo, M. Estrader,
S. Estradé, F.
Peiró, M. D. Baró, P. Sainctavit, P.Glatzel, and
J. Nogués, Nanoscale, 6,
Recently, the magnetic
anisotropies in a ferrofluid of
nanoparticles dispersed in heptane have been studied. Ferrofluids are
well-known for their
applications in optical waveguides, medicine (MRI, hyperthermia) or in
fine arts (photo below).
Their magnetic properties arise from both the magnetic anisotropies of
individual particles and the interparticular interactions that are mediated by the liquid
Using a specially-designed liquid cell (below), developed by
Niéli Daffé (PhD student LabEx MATISSE) and ID26
beamline of the ESRF (M. Rovezzi) we have
measured RIXS-MCD spectra and element selective hysteresis loops in the
phase and in the frozen phase. This has allowed investigating separately
the cationic distribution and magnetic anisotropies in the core and
the shell, as well as their mutual influence.
Sikora, N. Mas, V. Gavrilov, S.
Neveu, F. Choueikani, V. Dupuis, M. Rovezzi, Ph. Ohresser, Ph.
and A. Juhin, Advanced Materials Interfaces 22, 1700599 (2017) . Crédits
photos Niéli Daffé.