Electronic structure investigation of CoO by means of soft x-ray scattering

Magnuson, Martin; Butorin, Sergei M.; Guo, Jinghua; Nordgren, Joseph

doi:10.1103/physrevb.65.205106

Cited by 76 publications

(100 citation statements)

References 30 publications

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“…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.…”

Section: A Comparison With Inelastic X-rays and Optical Techniquessupporting

confidence: 86%

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

et al. 2013

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Neutron scattering is used to investigate the single-ion spin and orbital excitations below the Mott-Hubbard gap in CoO. Three excitations are reported at 0.870±0.009 eV, 1.84±0.03, and 2.30±0.15 eV. These were parameterized within a weak crystal field scheme with an intra-orbital exchange of J(dd)=1.3 ± 0.2 eV and a crystal field splitting 10Dq=0.94 ± 0.10 eV. A reduced spinorbit coupling of λ=-0.016± 0.003 eV is derived from dilute samples of Mg0.97Co0.03O, measured to remove complications due to spin exchange and structural distortion parameters which split the cubic phase degeneracy of the orbital excitations complicating the inelastic spectrum. The 1.84 eV, while reported using resonant x-ray and optical techniques, was absent or weak for non resonant x-ray experiments and overlaps with the expected position of a 4 A2 level. This transition is absent in the dipolar approximation but expected to have a finite quadrupolar matrix element that can be observed with neutron scattering techniques at larger momentum transfers. Our results agree with a crystal field analysis (in terms of Racah parameters and Tanabe-Sugano diagrams) and with previous calculations performed using local-density band theory for Mott insulating transition metal oxides. The results also demonstrate the use of neutron scattering for measuring dipole forbidden transitions in transition metal oxide systems.

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Section: A Comparison With Inelastic X-rays and Optical Techniquessupporting

confidence: 86%

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

et al. 2013

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“…The sample shows a completely different behavior after the application EF = -625 kV/cm for 10 min at 260 o C. The shoulder at 779.8 eV has turned into a peak. Two other peaks at 777.3 eV and 782.2 eV, characteristic of CoO [37], start to emerge, making the spectrum almost identical to that of CoO as previously reported [38]. Stronger evidence of a Co 2+ -dominating state is that the peaks at 778.6 eV and 779.8eV are nearly of the same height, consistent with a loss of metallic Co in the film [38,39].…”

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confidence: 78%

Reversible Control of Co Magnetism by Voltage-Induced Oxidation

et al. 2014

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We demonstrate that magnetic properties of ultra-thin Co films adjacent to Gd 2 O 3 gate oxides can be directly manipulated by voltage. The Co films can be reversibly changed from an optimallyoxidized state with a strong perpendicular magnetic anisotropy to a metallic state with an in-plane magnetic anisotropy, or to an oxidized state with nearly zero magnetization, depending on the polarity and time duration of the applied electric fields. Consequently, an unprecedentedly large change of magnetic anisotropy energy up to 0.73 erg/cm 2 has been realized in a nonvolatile manner using gate voltages of only a few volts. These results open a new route to achieve ultra-low energy magnetization manipulation in spintronic devices.

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“…The ionic bonding in GaN thus causes a low-energy chargetransfer satellite excitation as previously observed in insulating systems such as NiO and CoO. 40,41 This type of satellite can be reproduced using a ligand field treatment within the single impurity Anderson model ͑SIAM͒ including full multiplet configuration interaction to the Ga 4s 2 L −1 state, where L −1 denotes a hole in the N 2p ligand. The energy position of charge-transfer satellites appears about −1 eV lower than the normal emission band with the characteristics of delocalized states with almost constant emission energy as the excitation energy is changed.…”

Section: Discussionmentioning

confidence: 99%

Electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods

et al. 2010

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The electronic structure and chemical bonding of wurtzite-GaN investigated by N 1s soft x-ray absorption spectroscopy and N K, Ga M 1 , and Ga M 2,3 emission spectroscopy is compared to that of pure Ga. The measurements are interpreted by calculated spectra using first-principles density-functional theory ͑DFT͒ including dipole transition matrix elements and additional on-site Coulomb interaction ͑WC-GGA+ U͒. The Ga 4p-N 2p and Ga 4s-N 2p hybridization and chemical bond regions are identified at the top of the valence band between −1.0 and −2.0 and further down between −5.5 and −6.5 eV, respectively. In addition, N 2s-N 2p-Ga 4s and N 2s-N 2p-Ga 3d hybridization regions occur at the bottom of the valence band between −13 and −15 eV, and between −17.0 and −18.0 eV, respectively. A bandlike satellite feature is also found around −10 eV in the Ga M 1 and Ga M 2,3 emission from GaN, but is absent in pure Ga and the calculated ground-state spectra. The difference between the identified spectroscopic features of GaN and Ga are discussed in relation to the various hybridization regions calculated within band-structure methods.

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Electronic structure investigation of CoO by means of soft x-ray scattering

Cited by 76 publications

References 30 publications

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

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

Reversible Control of Co Magnetism by Voltage-Induced Oxidation

Electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods

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