Neutron Scattering from Magnetite below 119°K

Samuelsen, Emil J.; Bleeker, E. J.; Dobrzyński, L.; Riste, T.

doi:10.1063/1.1656188

Cited by 120 publications

(22 citation statements)

References 4 publications

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“…21,22 The observation of monoclinic lattice symmetry was also confirmed by a single-crystal x-ray study, 23 whereas the observation of a magnetoelectric effect indicated even lower P 1 symmetry in the low-temperature phase. 24 Although, clear evidence of the monoclinic lattice symmetry below T V was obtained, small atomic displacements have not been fully resolved so far.…”

Section: Introductionmentioning

confidence: 60%

Electronic structure of charge-orderedFe3O4from calculated optical, magneto-optical Kerr effect, and OK-edge x-ray absorption spectra

et al. 2006

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The electronic structure of the low-temperature (LT) monoclinic magnetite, Fe 3 O 4 , is investigated using the local spin density approximation (LSDA) and the LSDA+U method. The selfconsistent charge ordered LSDA+U solution has a pronounced [001] charge density wave character.In addition, a minor [00 1 2 ] modulation in the phase of the charge order (CO) also occurs. While the existence of CO is evidenced by the large difference between the occupancies of the minority spin t 2g states of "2+" and "3+" Fe B cations, the total 3d charge disproportion is small, in accord with the valence-bond-sum analysis of structural data. Weak Fe orbital moments of ∼0.07µ B are obtained from relativistic calculations for the CO phase which is in good agreement with recent x-ray magnetic circular dichroism measurements. Optical, magneto-optical Kerr effect, and O Kedge x-ray absorption spectra calculated for the charge ordered LSDA+U solution are compared to corresponding LSDA spectra and to available experimental data. The reasonably good agreement between the theoretical and experimental spectra supports the relevance of the CO solution obtained for the monoclinic LT phase. The results of calculations of effective exchange coupling constants between Fe spin magnetic moments are also presented.

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Section: Introductionmentioning

confidence: 60%

Electronic structure of charge-orderedFe3O4from calculated optical, magneto-optical Kerr effect, and OK-edge x-ray absorption spectra

et al. 2006

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“…There the formal valence of V ion is 3.5, and the one of Fe on B sites is 2.5 (the valence of Fe ions on A sites is 3), i.e., they have to exist in equal combinations of V 3+ and V 4+ , or Fe 2+ and Fe 3+ . Notice, however, that recent studies contradict the direct application of the ice (tetrahedron) rule to LiV 2 O 4 and Fe 3 O 4 [61,62,63,64,65,66,67,68,69,70,71,72,73,74,75]. For the recent reviews on spinel materials consult, e.g., [76,77,78,79].…”

Section: Ice Modelsmentioning

confidence: 99%

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

Zvyagin

2013

Low Temperature Physics

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During recent years the interest to frustrated magnets has grown considerably. Such systems reveal very peculiar properties which distinguish them from standard paramagnets, magnetically ordered regular systems (like ferro-, ferri-, and antiferromagnets), or spin glasses. In particular great amount of attention has been devoted to the socalled spin ices, in which magnetic frustration together with the large value of the single-ion magnetic anisotropy of a special kind, yield peculiar behavior. One of the most exciting features of spin ices is related to low-energy emergent excitations, which, from many viewpoints can be considered as analogies of Dirac's monopoles. In this article we review the main achievements of theory and experiment in this field of physics.

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“…In particular, the observation of half-integer reflections at (h, k, l + 1 2 ) points indicated the doubling of the unit cell along the c axis. 6 Further diffraction studies by neutron, 7,8 x-ray, 9 and electron 10 scattering established the monoclinic symmetry of the low temperature (LT) phase realized below T V . Indeed, the number of inequivalent A and B atomic positions found by nuclear magnetic resonance (NMR) for the phase below the VT 11,12,13 agrees with the monoclinic structure.…”

Section: Introductionmentioning

confidence: 99%

“…4 and Fe +2. 6 . Providing a convincing evidence in favor of such a state has been a challenge for several direct probing methods including the resonant xray scattering.…”

Section: Introductionmentioning

confidence: 99%

Origin of the Verwey transition in magnetite: Group theory, electronic structure, and lattice dynamics study

2007

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The Verwey phase transition in magnetite has been analyzed using the group theory methods. It is found that two order parameters with the symmetries X3 and ∆5 induce the structural transformation from the high-temperature cubic to the low-temperature monoclinic phase. The coupling between the order parameters is described by the Landau free energy functional. The electronic and crystal structure for the cubic and monoclinic phases were optimized using the ab initio density functional method. The electronic structure calculations were performed within the generalized gradient approximation including the on-site interactions between 3d electrons at iron ions -the Coulomb element U and Hund's exchange J. Only when these local interactions are taken into account, the phonon dispersion curves, obtained by the direct method for the cubic phase, reproduce the experimental data. It is shown that the interplay of local electron interations and the coupling to the lattice drives the phonon order parameters and is responsible for the opening of the gap at the Fermi energy. Thus, it is found that the metal-insulator transition in magnetite is promoted by local electron interactions, which significantly amplify the electron-phonon interaction and stabilize weak charge order coexisting with orbital order of the occupied t2g states at Fe ions. This provides a scenario to understand the fundamental problem of the origin of the Verwey transition in magnetite.

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Neutron Scattering from Magnetite below 119°K

Cited by 120 publications

References 4 publications

Electronic structure of charge-orderedFe3O4from calculated optical, magneto-optical Kerr effect, and OK-edge x-ray absorption spectra

Electronic structure of charge-orderedFe3O4from calculated optical, magneto-optical Kerr effect, and OK-edge x-ray absorption spectra

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

Origin of the Verwey transition in magnetite: Group theory, electronic structure, and lattice dynamics study

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