Exchange constants and transfer integrals of spinel ferrites

Bercoff, Paula G.; Bertorello, H.R.

doi:10.1016/s0304-8853(96)00748-2

Cited by 75 publications

(40 citation statements)

References 4 publications

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“…It is estimated that UЈ Ϸ 10 eV, UЉ Ϸ 8 eV, and b 2 Ϸ 0.1b 2 , 32,33 we then obtain the following ratios; 2J AB Ј / ͑J AB Ј + J AB Љ ͒ = 0.90, 2J AB Љ / ͑J AB Ј + J AB Љ ͒ = 1.10. Since the average AB superexchange is J AB = −4.8 meV in the cubic phase, we arrive at J AB Ј = −4.3 meV and J AB Љ = −5.3 meV.…”

Section: ͑27͒mentioning

confidence: 90%

Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum

et al. 2006

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Inelastic neutron scattering results on magnetite ͑Fe 3 O 4 ͒ show a large splitting in the acoustic spin wave branch, producing a 7 meV gap midway to the Brillouin zone boundary at q = ͑0,0,1/2͒ and ប = 43 meV. The splitting occurs below the Verwey transition temperature, where a metal-insulator transition occurs simultaneously with a structural transformation, supposedly caused by the charge ordering on the iron sublattice. The wavevector ͑0,0,1/2͒ corresponds to the superlattice peak in the low symmetry structure. The dependence of the magnetic superexchange on changes in the crystal structure and ionic configurations that occur below the Verwey transition affect the spin wave dispersion. To better understand the origin of the observed splitting, several Heisenberg models intended to reproduce the pair-wise variation of the magnetic superexchange arising from both small crystalline distortions and charge ordering were studied. None of the models studied predicts the observed splitting, whose origin may arise from charge-density wave formation or magnetoelastic coupling.

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Section: ͑27͒mentioning

confidence: 90%

Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum

et al. 2006

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“…These properties result from many variations of the magnetic and nonmagnetic ions that can be accommodated on the tetrahedral A sites and the octahedral B sites in the AB 2 O 4 spinel structure, thus affecting the magnitudes of the superexchange interactions J AA , J BB , and J AB [7][8][9]. The presence of nonmagnetic ions on either the A or the B sites can lead to magnetic frustration [10][11][12] [13], which have magnetic ions only on the B sites with ' ' as vacancy, the magnetic ground state is highly frustrated, as first predicted by Anderson in such a case [14].…”

Section: Introductionmentioning

confidence: 99%

Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering inCo2TiO4

et al. 2015

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The complex nature of magnetic ordering in the spinel Co 2 TiO 4 is investigated by analyzing the temperature and magnetic field dependence of its magnetization (M), specific heat (C p ), and ac magnetic susceptibilities χ and χ . X-ray diffraction of the sample synthesized by the solid-state reaction route confirmed the spinel structure whereas x-ray photoelectron spectroscopy shows its electronic structure to be

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“…50 In a recent attempt to compare this theory with the theory of superexchange one even had to assume the exchange field at the A sites to be zero. 51 Moreover, the influence of charge transfer was neglected, which could be especially important for the second halve of the first row TM oxides. 52 The model which leads to the full CF Hamiltonian presented in Sec.…”

Section: Discussionmentioning

confidence: 99%

Single-ion anisotropy of localized-electron compounds

2001

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We present a computational analysis of the influence of taking the full multiplet structure into account in calculations of the single-ion contribution to the magnetocrystalline anisotropy ͑MCA͒ of 3d transition-metal ͑TM͒ ions in localized-electron compounds at Tϭ0 K. For atoms with d n (nϭ1 -4,6-9) configurations, at sites with a local cubic, tetragonal, or trigonal symmetry the single ion MCA on the basis of the Hund's rule ground state term only ͓crystal field ͑CF͒ theory͔ is compared with the single-ion MCA on the basis of a fully relativistic first principles atomic theory including the intra-atomic d-d interaction. Solid state effects are taken into account by effective crystal fields and the exchange field. Under certain, realistic, conditions the use of the full multiplet theory is shown to have a significant effect on the calculated single-ion MCA. We also discuss the effect on the overall cubic anisotropy constants for cubic crystals containing transition metal atom sublattices for which the d-metal atoms are located on sites with a local tetragonal and trigonal symmetry. Possible refinements of the theory are discussed.

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Exchange constants and transfer integrals of spinel ferrites

Cited by 75 publications

References 4 publications

Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum

Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum

Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering inCo2TiO4

Single-ion anisotropy of localized-electron compounds

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