Experimental techniques

- resonant inelastic x-ray scattering (RIXS)

- x-ray absorption spectroscopy (XAS)

- x-ray photoelectron spectroscopy (XPS)

- angle resolved photoemission spectroscopy (ARPES)

Areas of expertise

- strongly correlated electron systems

- molecular magnetism

- soft x-ray grating spectrometers & beamlines

Research highlights

Spin flip excitations without spin-orbit coupling in the core-hole state

Resonant inelastic x-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin–orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr2IrO4, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edge RIXS energy resolution in the hard x-ray region is usually poor.

Fig. Momentum dependence of the RIXS spectra with p incident polarization.

Related publication:

Probing single magnon excitations in Sr2IrO4 using O K-edge resonant inelastic x-ray scattering
X. Liu, M. P. M. Dean, J. Liu, S. G. Chiuzbăian, N. Jaouen, A. Nicolaou, W. G. Yin, C. Rayan Serrao, R. Ramesh, H. Ding and J. P. Hill
Journal of Physics : Condensed Matter 27, 202202 (2015)

Joint resonant inelastic x-ray scattering studies of 3d transition metal compounds: the CoO case

We performed resonant inelastic x-ray scattering (RIXS) measurements jointly across the M2,3 and L3 absorption thresholds in order to study CoO local electronic structure. Our high-resolution experimental data are supported by state-of-the-art model calculations: the same core-hole independent set of parameters is used within the single impurity Anderson model is used to describe both the M (3p-3d) and L (2p-3d). Measured M2,3-RIXS spectra are observed to be free of charge-transfer or normal fluorescence contributions. Moreover the cross section of M-RIXS final states with change in spin multiplicity is low. Combining this information with L-edge studies establishes an appealing means of making a better separation between on-site and intersite ligand to metal electronic excitations. Experimental and theoretical features specific to RIXS studies performed at M and L edges are summarized as a basis for future studies on complex transition metal compounds.

Fig. CoO RIXS measurements displayed after substraction of the elastic peak.

Related publication:

Combining M- and L-edge resonant inelastic x-ray scattering for studies of 3d transition metal compounds
S.G. Chiuzbăian, T. Schmitt, M. Matsubara, A. Kotani, G. Ghiringhelli, C. Dallera, A. Tagliaferri, L. Braicovich, V. Scagnoli, N. B. Brookes, U. Staub and L. Patthey
Physical Review B 78, 245102 (2008)

First evidence of spin flip excitations with resonant inelastic x-ray scattering

We studied the neutral electronic excitations of NiO localized at the Ni sites by measuring the resonant inelastic x-ray scattering (RIXS) spectra at the Ni M2,3 edges. The good energy resolution allows an unambiguous identification of several spectral features due to dd excitations. The dependence of the RIXS spectra on the excitation energy gives evidence of local spin flip and yields a value of 125±15 meV for the antiferromagnetic exchange interaction. Accurate crystal field parameters are also obtained.

Fig. X-ray scattering results for NiO with incoming photon energies encompassing Ni M absorption edges. The spectra deliver information on the crystal-field and the magnetic exchange energy between Ni ions.

Related publication:

Localized Electronic Excitations in NiO Studied with Resonant Inelastic X-Ray Scattering at the Ni M Threshold: Evidence of Spin Flip
S.G. Chiuzbăian, G. Ghiringhelli, C. Dallera, M. Grioni, P. Amann, X. Wang, L. Braicovich and L. Patthey
Physical Review Letters 95, 197402 (2005)