Reexamination of the Temperature Dependences of Resonant Reflections in Highly Stoichiometric Magnetite

García, José Rodríguez; Subı́as, G.; Herrero‐Martín, Javier; Blasco, Javier; Cuartero, Vera; Sánchez, M. C.; Mazzoli, Claudio; Yakhou, F.

doi:10.1103/physrevlett.102.176405

Cited by 31 publications

(51 citation statements)

References 23 publications

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“…The resonant and nonresonant signals simultaneously disappear at T v (±0.5 K) and the intensity of all these reflections is zero at temperatures above 125 K. This result shows that RXS in Fe 3 O 4 comes from the ordering of local distortions at the structural transition, which leads to an ordered formal charge segregation and electronic anisotropy at the Fe atoms [15].…”

Section: Resonant Effects Due To Different Crystallographic Sites (Chmentioning

confidence: 76%

“…We examine now the limit for the possible charge segregation over the octahedral atoms along the c axis given by the sensitivity of the RXS technique in a highly stoichiometric single crystal of Fe 3 O 4 (T V =123.5 K) [15]. Figure 2 (left panel) shows the energy dependence of the intensities for some characteristic Bragg and forbidden reflections at the Fe K-edge and at 60 K compared to the fluorescence spectrum.…”

Section: Resonant Effects Due To Different Crystallographic Sites (Chmentioning

confidence: 99%

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Resonant x-ray scattering in 3d-transition-metal oxides: Anisotropy and charge orderings

Subı́as

Garcı́a

Blasco

et al. 2009

J. Phys.: Conf. Ser.

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The structural, magnetic and electronic properties of transition metal oxides reflect in atomic charge, spin and orbital degrees of freedom. Resonant x-ray scattering (RXS) allows us to perform an accurate investigation of all these electronic degrees. RXS combines high-Q resolution x-ray diffraction with the properties of the resonance providing information similar to that obtained by atomic spectroscopy (element selectivity and a large enhancement of scattering amplitude for this particular element and sensitivity to the symmetry of the electronic levels through the multipole electric transitions). Since electronic states are coupled to the local symmetry, RXS reveals the occurrence of symmetry breaking effects such as lattice distortions, onset of electronic orbital ordering or ordering of electronic charge distributions. We shall discuss the strength of RXS at the K absorption edge of 3d transition-metal oxides by describing various applications in the observation of local anisotropy and charge disproportionation. Examples of these resonant effects are (I) charge ordering transitions in manganites, Fe 3 O 4 and ferrites and (II) forbidden reflections and anisotropy in Mn 3+ perovskites, spinel ferrites and cobalt oxides. In all the studied cases, the electronic (charge and/or anisotropy) orderings are determined by the structural distortions.

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Section: Resonant Effects Due To Different Crystallographic Sites (Chmentioning

confidence: 76%

Section: Resonant Effects Due To Different Crystallographic Sites (Chmentioning

confidence: 99%

Resonant x-ray scattering in 3d-transition-metal oxides: Anisotropy and charge orderings

Subı́as

Garcı́a

Blasco

et al. 2009

J. Phys.: Conf. Ser.

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“…Group B, instead, is made of octahedrally coordinated sites formally occupied by Fe 3+ B (3d 5 , S=5/2) and Fe 2+ B (3d 6 , S=2) ions. At T c = 858 K, ferrimagnetic order sets in with ferromagnetic coupling within the B sublattice and antiferromagnetic coupling between A and B sites such that the A sites carry minority spins ↓.…”

Section: +mentioning

confidence: 99%

Phase separation in the nonequilibrium Verwey transition in magnetite

et al. 2016

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We present equilibrium and out-of-equilibrium studies of the Verwey transition in magnetite. In the equilibrium optical conductivity, we find a step-like change at the phase transition for photon energies below about 2 eV. The possibility of triggering a non-equilibrium transient metallic state in insulating magnetite by photo excitation was recently demonstrated by an x-ray study. Here we report a full characterization of the optical properties in the visible frequency range across the nonequilibrium phase transition. Our analysis of the spectral features is based on a detailed description of the equilibrium properties. The out-of-equilibrium optical data bear the initial electronic response associated to localized photo-excitation, the occurrence of phase separation, and the transition to a transient metallic phase for excitation density larger than a critical value. This allows us to identify the electronic nature of the transient state, to unveil the phase transition dynamics, and to study the consequences of phase separation on the reflectivity, suggesting a spectroscopic feature that may be generally linked to out-of-equilibrium phase separation.

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“…Single crystals showed a saturation magnetization at 5 K of 4.11μ B , and T V is 123.5 K with a narrow transition width ( T = 1 K). 26 These features correspond to highly stoichiometric samples, Fe 3(1−δ) O 4 with δ ∼ = 0.000. 24,27,28 Synchrotron x-ray diffraction patterns were measured at the ID31 beamline at the ESRF (Grenoble, France).…”

Section: Methodsmentioning

confidence: 99%

Structural transformation in magnetite below the Verwey transition

2011

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The magnetite structure was studied with synchrotron x-ray powder diffraction above and below the Verwey transition. A symmetry-mode analysis was performed to obtain the atomic displacements from the amplitudes of condensing modes. The main contributing modes that drive the structural phase transition at the Verwey temperature correspond to the irreducible representations 5 , X 1 , X 4 , W 1 , and W 2 . The W modes, neglected so far, must be taken into account so a reliable description of the low-temperature crystal structure can be obtained. This is refined in the nonpolar space group C2/c with ten nonequivalent octahedral irons. The condensation of the mentioned modes leads to a wide distribution of local environments around the octahedral iron atoms, whose valences range between 2.53 and 2.84. This finding rules out any bimodal charge disproportionation of the octahedral iron atoms, i.e., an Fe 2+ -like/Fe 3+ -like ordering.

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Reexamination of the Temperature Dependences of Resonant Reflections in Highly Stoichiometric Magnetite

Cited by 31 publications

References 23 publications

Resonant x-ray scattering in 3d-transition-metal oxides: Anisotropy and charge orderings

Resonant x-ray scattering in 3d-transition-metal oxides: Anisotropy and charge orderings

Phase separation in the nonequilibrium Verwey transition in magnetite

Structural transformation in magnetite below the Verwey transition

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