CombiningM- andL-edge resonant inelastic x-ray scattering for studies of3dtransition metal compounds

Abstract

Resonant inelastic x-ray scattering ͑RIXS͒ measurements performed jointly across the M 2,3 and L 3 absorption thresholds are used to study CoO local electronic structure and are supported by model calculations. The high-resolution experimental data provide a precise set of parameters to describe the correlated response of valence electrons. The same core-hole independent set of parameters within the single impurity Anderson model is used to describe both the M ͑3p-3d͒ and L ͑2p-3d͒ resonances. This work shows that combining M and L scattering data provides an enhanced contrast view of the spectral weights. Measured M 2,3 -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 metal͒ 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.

Neutron scattering investigation of thed−dexcitations below the Mott gap of CoO

“…The 0.870 and 2.3 eV peaks are in agreement with x-rays but the 1.84 eV excitation was not resolved with non-resonant xrays and is forbidden in the dipolar approximation, however it has been reported in other optical and x-ray studies such as RIXS and EELS that are sensitive to dipole forbidden cross sections. 38,[43][44][45][46][47] This result highlights the point that the 1.84 ±0.03 eV excitation is dipole forbidden and confirms our claim that we are sampling a quadrupolar matrix element in our neutron scattering experiments.…”

Extending resonant inelastic X-ray scattering to the extreme ultraviolet

“…These effects will be discussed in Sections 5, 6. Many of our observations about EUV RIXS in this paper are common with earlier studies, and in particular the insightful discussion in Chiuzbaian et al [16]. However, we have attempted to consider a wider range of effects and provide a broader context with respect to numerics.…”

“…The reason the EUV M-edge has the least contraction is that the radial part of the core orbital wavefunction for shallow core holes is quite similar to the radial wavefunction of valence electrons, meaning that the total radial charge density distribution surrounding the scattering site is not greatly disrupted in resonance states. A weak core hole potential has also been proposed in Chiuzbaian et al [16] to explain the lack of charge transfer excitations in M-edge RIXS on CoO.…”

“…The principle electronic excitations observed in Xray absorption spectroscopy (XAS) and RIXS with p-symmetry core holes on Co [7,16], Ni [6,8,14,15,17,18,36], and Cu [8,9] are closely identified with excitation matrix elements obtained from AM based calculations for a high-spin 2+ valence atomic state perturbed by the crystal field of surrounding oxygen atoms. The compounds CoO and NiO have a rock salt crystal structure, with an octahedral crystal field on the transition metal site, and strong antiferromagnetic superexchange interactions through σ -bonded oxygen atoms.…”

“…Previous experimental studies performed with soft X-rays at the transition metal L-edge (700-900 eV) have noted that charge transfer features from these materials have significant intensity at 4-7 eV energy loss [14,[16][17][18]. M-edge studies have noted that charge transfer excitations are weak, but stopped short of presenting data that covered the Mott gap feature [15,16]. Broadrange M-edge RIXS resonance profiles of CoO and NiO are shown in Figure 3, including energies above the insulating gap.…”