02.06.2016

„Hard X-ray RIXS-MCD, a magnetic spectroscopy for in situ characterization of nanoparticles and ferrofluids” – seminarium ACMiN


Akademickie Centrum Materiałów i Nanotechnologii AGH zaprasza na seminarium, które odbędzie się 2 czerwca 2016 r. o godz. 15.00.

Referat pod tytułem „Hard X-ray RIXS-MCD, a magnetic spectroscopy for in situ characterization of nanoparticles and ferrofluids” wygłosi Dr Amélie Juhin (Institut de Mineralogie, Physique des Materiaux et Cosmochimie, Universite Pierre et Marie Curie-CNRS, Paris, France).

Miejsce: ul. Kawiory 30, bud. D-16, sala audytoryjna ACMiN (1.02A).

Dr Amelie Juhin jest ekspertem w dziedzinie spektroskopii absorpcji i emisji promieniowania X, z powodzeniem łączącym badania eksperymentalne i teoretyczne. Za wkład do teorii procesów absorpcji rentgenowskiej w monokryształach została uhonorowana nagrodą IXAS Outstanding Young Scientist Award 2015. Seminarium będzie poświęcone jej obecnym zainteresowaniom naukowym - badaniu morfologii nanocząstek typu core/shell/shell i anizotropii magnetycznej ferrofluidów.

„Hard X-ray RIXS-MCD, a magnetic spectroscopy for in situ characterization of nanoparticles and ferrofluids”

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 self-absorption effects) with the high resolution of RIXS.

Recently, it was shown that hard x-ray RIXS-MCD can be a valuable alternative to soft x-ray XMCD, when using demanding sample environments, such as liquids and gas cells, or when investigating materials whose surface may not be representative of bulk properties [1]. Additionally, the 2D character (photon-in, photon-out) of RIXS-MCD enables to better disentangle the spectroscopic signatures of different valences. This technique has first been used to characterize crystals and multilayered thin films, and recently it was used for the first time on magnetic nanoparticles. In this talk, two examples will illustrate the new possibilities offered by RIXS-MCD in this research field.

First, we have investigated bi-magnetic core-shell nanoparticles, which currently focus high interest owing to their applications in biomedicine (hyperthermia, highly sensitive biosensors, improved MRI...) and technology (magnetic recording, permanent 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 nanoparticles, RIXS-MCD gives the smoking gun evidence for the existence of a magnetic interdiffused inner shell of (Mn,Fe) spinel growing from the core γ-Fe2O3 and the shell Mn3O4. Combined with TEM-EELS experiments, a quantitative multilayered “onion” structure is proposed, which allows understanding the influence of the interface quality on the measured magnetic properties [2].

Second, we have studied the magnetic anisotropies in a ferrofluid of monodispersed core@shell nanoparticles dispersed in heptane. Ferrofluids are well-known for their applications in optical waveguides, medicine (MRI, hyperthermia) or in fine arts. Their magnetic properties arise from both the magnetic anisotropies of individual particles and the interparticular interactions that are mediated by the liquid carrier. Using a specially-designed liquid cell, we have measured RIXS-MCD spectra and element selective hysteresis loops in the liquid phase and in the frozen phase. This allowed investigating separately the cationic distribution and magnetic anisotropies in the core and those in the shell, as well as their mutual influence [3].

References:

[1]-M. Sikora, A. Juhin, T.-S.Weng, Ph. Sainctavit, C. Detlefs, F. M. F. de Groot, and P. Glatzel, Physical Review Letters 105, 037202 (2010).
[2]- A. Juhin, A. Lopez-Ortega, M. Sikora, C. Carvallo, M. Estrader, S. Estrade, F. Peiro, M. D. Baro, P. Sainctavit, P.Glatzel, and J. Nogues, Nanoscale, 6, 11911-11920 (2014).
[3]- N. Daffe, M. Sikora, N. Mas, V. Gavrilov, S. Neveu, F. Choueikani, V. Dupuis, M. Rovezzi, Ph. Sainctavit and A. Juhin, in preperation.