Charge ordering and elastic constants in Fe Zn O

Schwenk, H.; Bareiter, S.; Hinkel, C.; Lüthi, B.; Ka̧kol, Z.; Koslowski, A.; Honig, J. M.

doi:10.1007/s100510050060

Cited by 46 publications

(47 citation statements)

References 17 publications

(28 reference statements)

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“…The derived values of the inplane and out-of-plane strain yield a Poisson ratio of 0.33, which is in good agreement with Ref. 78. In contrast to the x-ray measurements at E z = 400 kV/m, the intensity of the Fe 3 O 4 (004) reflection at E z = 0 kV/m is strongly reduced and a second peak occurs close to the first one [ Fig.…”

Section: Two Region Modelsupporting

confidence: 69%

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Converse magnetoelectric effects in Fe3O4/BaTiO3multiferroic hybrids

et al. 2013

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The quantitative understanding of converse magnetoelectric effects, i.e., the variation of the magnetization as a function of an applied electric field, in extrinsic multiferroic hybrids is a key prerequisite for the development of future spintronic devices. We present a detailed study of the strain-mediated converse magnetoelectric effect in ferrimagnetic Fe3O4 thin films on ferroelectric BaTiO3 substrates at room temperature. The experimental results are in excellent agreement with numerical simulation based on a two-region model. This demonstrates that the electric field induced changes of the magnetic state in the Fe3O4 thin film can be well described by the presence of two different ferroelastic domains in the BaTiO3 substrate, resulting in two differently strained regions in the Fe3O4 film with different magnetic properties. The two-region model allows to predict the converse magnetoelectric effects in multiferroic hybrid structures consisting of ferromagnetic thin films on ferroelastic substrates.

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Section: Two Region Modelsupporting

confidence: 69%

“…78 The interaction between the elastic and the magnetic anisotropy energies is described by the first order magnetoelastic energy density u • between the sample normal and the rotation axis.…”

Section: Magnetoelastic Effectsmentioning

confidence: 99%

Converse magnetoelectric effects in Fe3O4/BaTiO3multiferroic hybrids

et al. 2013

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“…In particular, the term dg 2 in the last line, describing the coupling between the X 3 and T 2g OPs, contributes to the softening of the c 44 elastic constant. 36 Other couplings involving the zone-center IRs may account for anomalies observed by the Raman studies.…”

Section: B Free Energy Functionalmentioning

confidence: 99%

“…The pronounced softening of the c 44 elastic constant, 35 observed from room temperature down to T V , has been explained by the coupling between the shear mode and the charge-density T 2g order parameter (OP) at the Γ point. 36 The decrease of c 44 is associated with the softening of the surface Rayleigh mode observed by the Brillouin scattering. 37 In the bulk, no phonon softening has been observed, 38 however, critical fluctuations revealed by neutron scattering strongly indicate the existence of phonon precursor effects which drive the structural deformation.…”

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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“…Recent band-structure calculations including Coulomb interelectron correlations yielded an insulating gap comparable to that experimentally measured [8,9]. Apart from the indirect suggestions on lattice dynamics changing [10,11], recently, the lattice stiffening below T V was directly proved [12]. Consequently, electrons confined to lattice creating small polarons were successfully used to reproduce temperature dependence of resistivity [13].…”

Section: Introductionmentioning

confidence: 85%

Electronic states of magnetite from photoemission spectroscopy ARUPS

Zalecki

Kołodziejczyk

Kozłowski

et al. 2006

Physica Status Solidi (b)

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The valence band photoemission spectra of epitaxially grown film and bulk single crystal of magnetite were measured by the angle-resolved ultraviolet photoemission spectroscopy (ARUPS) at 300 K and 120 K. Four main features of the electron photoemission were observed at about -1.0 eV, -3.5 eV, -5.0 eV and -6.5 eV below the chemical potential; they are rather strongly dependant on structure and preparation of surface. The three higher-energy features showed significant energy dispersion. The ARUPS spectra were compared to the accessible band structure calculations. Special attention was paid to the leading edge of the emission at -1.0 eV of the low-temperature spectrum where an insulating gap should be observed.

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Charge ordering and elastic constants in Fe Zn O

Cited by 46 publications

References 17 publications

Converse magnetoelectric effects in Fe3O4/BaTiO3multiferroic hybrids

Converse magnetoelectric effects in Fe3O4/BaTiO3multiferroic hybrids

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

Electronic states of magnetite from photoemission spectroscopy ARUPS

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