Calculated electronic structure and x-ray magnetic circular dichroism of CrO<sub>2</sub>

Kanchana, V.; Vaitheeswaran, G.; Alouani, M.

doi:10.1088/0953-8984/18/22/015

Cited by 22 publications

(18 citation statements)

References 63 publications

(130 reference statements)

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“…CrO [5] the ratio of the 2 L XMCD peak to the 3 L peak is of the order of magnitude of -1, whereas in our model calculation it is zero in linear order of B . The importance of the density of states in real materials is further underpinned by the fact that the band-structure theory explains the two structures present in both the 2 L and 3 L parts of the XMCD spectrum of Cr in 2 CrO in terms of the two first peaks, respectively, in the density of states of the two spin channels just above the Fermi level [5].…”

Section: Resultscontrasting

confidence: 46%

“…The importance of the density of states in real materials is further underpinned by the fact that the band-structure theory explains the two structures present in both the 2 L and 3 L parts of the XMCD spectrum of Cr in 2 CrO in terms of the two first peaks, respectively, in the density of states of the two spin channels just above the Fermi level [5]. Thus, the one-electron model misses an essential ingredient for the description of magnetic dichroism in real materials, and it should not be overestimated with respect to its ability to interpret experimental results.…”

Section: Resultsmentioning

confidence: 99%

“…To describe the XMCD effect quantitatively requires sophisticated band-structure calculations which deal with the complicated relativistic many-electron problem within the framework of the density functional electron theory. For examples, we refer to the calculation of the XMCD effect at the 2 L -and 3 L -edges of Fe and Fe nitrides [4] as well as of Cr in 2 CrO [5] by the relativistic all-electron full potential linear muffin-tin orbital method. In theoretical physics, however, it is desirable to describe a very complicated situation by a simple model which encompasses the essential physics of the problem.…”

Section: Introductionmentioning

confidence: 99%

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Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Rodríguez

Kostoglou

Singer

et al. 2008

Physica Status Solidi (b)

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The magnetic dichroism, i.e., the difference in the absorption coefficient for right‐ and left‐circularly polarized electromagnetic waves, is a relativistic many‐electron effect in a magnetic material. Jenkins and Strange have introduced the most simple and analytically solvable quantum mechanical model which exhibits magnetic dichroism, i.e., the relativistic one‐electron atom in an external magnetic field. We have extended this model by considering the 2p–3d transitions and by taking into account the effect of an additional crystal field. The model predicts near‐zero dichroism for the 2p1/2–3d3/2 transition (L2‐absorption) if the crystal field and the effect of the magnetic field on the core states are neglected, in contrast to the strong dichroism for the L2‐absorption in real materials. The reason for this limitation of the model of Jenkins and Strange is discussed. The j –j mixing of the initial states by the additional crystal field potential has some weak effect on the dichroism. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Resultscontrasting

confidence: 46%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Rodríguez

Kostoglou

Singer

et al. 2008

Physica Status Solidi (b)

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“…By computing the XMCD spectra from density functional theory, it becomes possible to distinguish between the Fe signals from different sites, aiding the interpretation of the experimental XMCD spectra. Further, Kanchana et al 3 have investigated the effect of magnetic anisotropy on XMCD spectra of CrO 2 . They found that the computed XMCD anisotropy is much smaller than the measured one.…”

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confidence: 99%

Electronic structure and x-ray magnetic circular dichroism ofSr2FeMoO6:Ab initiocalculations

et al. 2007

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Theoretical investigations of the electronic structure, x-ray absorption, and x-ray magnetic circular dichroism ͑XMCD͒ at the Fe L 2,3 and Mo L 2,3 edges of Sr 2 FeMoO 6 are carried out by means of the generalized gradient approximation. The magnetic coupling between Fe and Mo is found to be antiparallel, which gives direct confirmation of ferrimagnetic ordering and settles controversies existing between the earlier experimental reports. This is also confirmed by our good agreement of the Mo L 2,3 edges with experiment. Using our theoretical spectra, we recalculate the spin and orbital magnetic moments by means of the XMCD sum rules and compare the results with a direct self-consistent calculation and experiment. Soft x-ray magnetic circular dichroism ͑XMCD͒, which initially was viewed as quite an exotic technique, has now developed into a standard experimental tool in the exploration of magnetic and electronic properties, with atomic and orbital selectivity. With the help of the sum rules derived by Thole and co-workers, 1 the spin and orbital moments for all inequivalent sites in a crystal can be computed directly from the XMCD spectra. The results from XMCD measurements can be combined in several useful ways with density functional theory. For example, the calculation by Antonov et al. 2 of the XMCD spectra of magnetite Fe 3 O 4 , which is a mixed valent material with both Fe 2+ and Fe 3+ ions present, showed that Fe atoms occupy two types of sites, tetrahedral ones, called A, and octahedral ones, called B. All the A sites are occupied by Fe 3+ , whereas at the B sites there is a mix of Fe 2+ and Fe 3+ . By computing the XMCD spectra from density functional theory, it becomes possible to distinguish between the Fe signals from different sites, aiding the interpretation of the experimental XMCD spectra. Further, Kanchana et al. 3 have investigated the effect of magnetic anisotropy on XMCD spectra of CrO 2 . They found that the computed XMCD anisotropy is much smaller than the measured one.Sr 2 FeMoO 6 ͑SFMO͒ is a case of special interest due to its technological potential as a spintronics material, and due to the many diverging reports, both theoretical and experimental, on its electronic and magnetic structure. SFMO is a magnetic metal with a gap in one spin channel, i.e., it is a socalled half metal with a Curie temperature T C of 418 K, exceeding room temperature. The half metallicity causes total spin polarization of the charge carriers. This, in turn, may give rise to a low-field magnetoresistive effect based on intergrain tunneling, which can be explained in a simple model as follows. In a system with a microstructure consisting of half-metallic monodomain grains dispersed in an insulating matrix, the magnetic moments of the magnetic grains are randomly ordered, and the tunneling from grain to grain becomes low, since the moments of two adjacent grains in general are not aligned. As the grain magnetic moments align due to an increasing external magnetic field, the resistance is reduced. Note that there is...

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“…Recent theoretical work has suggested that self-doping generates the mixed valence state of Cr ions and the oxygen-mediated DE interaction [3,4]: Korotin et al revealed that the t 2g orbitals of Cr ions in CrO 6 octahedra are split into an xy localized state and xz yz itinerant states and that Cr3d-O2p hybridization induces a mixed valence state of Cr ions [3]. The hybridization that supports self-doping has been observed through experiments such as resonant photoemission and x-ray absorption spectroscopy [5][6][7][8]. The Hall resistivity measurement has suggested 0.3-0.4 charge carriers per formula unit of CrO 2 [9,10].…”

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confidence: 99%

Coexistence of Two Different Cr Ions by Self-Doping in Half-MetallicCrO2Nanorods

et al. 2007

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We investigated the physical properties of Cr ions in half-metallic CrO(2) using 53Cr nuclear magnetic resonance (NMR). The 53Cr NMR spectra showed two peaks with a similar intensity instead of the single peak anticipated from a uniform single valence Cr(+4). Both Cr peaks exhibited a strong anisotropy in the hyperfine field and similar values in the enhancement factor and T2 relaxation time. These results suggest the coexistence of two different Cr ions (provisionally, Cr(+4 +/- 1/3)) by a self-doping effect, which is a likely origin of the metallic ferromagnetism in CrO(2).

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Calculated electronic structure and x-ray magnetic circular dichroism of CrO₂

Cited by 22 publications

References 63 publications

Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Electronic structure and x-ray magnetic circular dichroism ofSr2FeMoO6:Ab initiocalculations

Coexistence of Two Different Cr Ions by Self-Doping in Half-MetallicCrO2Nanorods

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Calculated electronic structure and x-ray magnetic circular dichroism of CrO2

Cited by 22 publications

References 63 publications

Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one‐electron atom

Electronic structure and x-ray magnetic circular dichroism ofSr2FeMoO6:Ab initiocalculations

Coexistence of Two Different Cr Ions by Self-Doping in Half-MetallicCrO2Nanorods

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Calculated electronic structure and x-ray magnetic circular dichroism of CrO₂