Magneto-optical study of the Verwey transition in magnetite

Neal, James R.; Behan, A.J.; Mokhtari, Abbas; Ahmed, Mahrous R.; Blythe, H. J.; Fox, A. M.; Gehring, G. A.

doi:10.1016/j.jmmm.2006.10.132

Cited by 8 publications

(12 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The structural and magnetic properties of these NPs were described in [14] as it was mentioned above. The spectra of all these samples demonstrate the same shape very similar to the magnetite, Fe 3 O 4 , MCD spectrum shape known in literature [37][38][39][40].…”

Section: Magnetic Circular Dichroism Measurementssupporting

confidence: 80%

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag

et al. 2020

View full text Add to dashboard Cite

Core-shell Fe x O y @C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer spectroscopy, static magnetic measurements, and optical magnetic circular dichroism (MCD). Fe x O y @C NPs synthesized by the pyrolysis process of the mixture of Fe(NO 3 ) 3 • 9H 2 O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO 3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe 3 O 4 and γ-Fe 2 O 3 . Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid Fe x O y @C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe 3 O 4 @C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the Fe x O y @C-Ag NPs is discussed.

show abstract

Section: Magnetic Circular Dichroism Measurementssupporting

confidence: 80%

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag

et al. 2020

View full text Add to dashboard Cite

show abstract

“…31 The obtained magnitude of the insulating gap agrees well with the photoemision data below T V . 32,33,34 On the contrary, in absence of electron interactions (for U = 0) the electronic state remains metalic even in the distorted structure, showing the essential role played by local electron interactions in the VT.…”

Section: Introductionsupporting

confidence: 84%

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

2007

View full text Add to dashboard Cite

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.

show abstract

“…The signal at $ 2 eV is believed to originate from a transition between the occupied part of the minority t 2g band to a state in the minority e g band, while the signal at $3 eV is believed to be an inter-site transition from an A site to the unoccupied part of the minority t 2g band on the B site. The energies at which the amplitude of these two signals have their maximum value show small shifts with temperature [4], as shown for the peak near 2 eV in the lower panel of Fig. 5.…”

Section: Magneto-optic Measurements Of Fe 3 Omentioning

confidence: 66%

“…This is about half of the low temperature energy gap of 0.06 eV [4], and is a rather elegant demonstration of the splitting of the minority t 2g band caused by the distortion.…”

Section: Magneto-optic Measurements Of Fe 3 Omentioning

confidence: 73%

See 1 more Smart Citation

Magneto-optic studies of magnetic oxides

Gehring

Alshammari

Score

et al. 2012

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

Magneto-optical study of the Verwey transition in magnetite

Cited by 8 publications

References 4 publications

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag

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

Magneto-optic studies of magnetic oxides

Contact Info

Product

Resources

About

Magneto-optical study of the Verwey transition in magnetite

Cited by 8 publications

References 4 publications

Characterization of the iron oxide phases formed during the synthesis of core–shell FexOy@C nanoparticles modified with Ag

Characterization of the iron oxide phases formed during the synthesis of core–shell FexOy@C nanoparticles modified with Ag

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

Magneto-optic studies of magnetic oxides

Contact Info

Product

Resources

About

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag

Characterization of the iron oxide phases formed during the synthesis of core–shell Fe_xO_y@C nanoparticles modified with Ag