Defects and the electronic properties of Y3Fe5O12

Larsen, P.K.; Metselaar, R Ruud

doi:10.1016/0022-4596(75)90315-1

Cited by 43 publications

(14 citation statements)

References 13 publications

(5 reference statements)

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“…Nevertheless, it has been shown that in some iron oxides, including LiFe 5 O 8 and GaFeO 3 , apparently forbidden crystal field d – d transitions may become allowed through antiferromagnetic spin coupling between next-nearest neighbor Fe atoms . According to literature reports, absorption bands at wavelengths below 413 nm can be ascribed to both oxygen-to-iron and oxygen-to-yttrium charge transfer (CT) as well as intervalence transitions between Fe 3+ ions on the tetrahedral and octahedral sites. − The optical band gap at room temperature was found to lie in the range 2.6–2.9 eV and has been shown to arise due to excitation from O 2p valence band to Fe oct 3d conduction band. − For this reason, YIG is referred to as a charge-transfer insulator. We estimate the band gap energy, E g , from the data for a direct transition as being (2.84 ± 0.05) eVthe lack of the characteristic shape of the plot α 1/2 versus photon energy argues against an indirect optical transition in the KLE-templated YIG thin films.…”

Section: Resultsmentioning

confidence: 99%

Room Temperature Magnetic Rare-Earth Iron Garnet Thin Films with Ordered Mesoporous Structure

et al. 2013

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Amphiphilic polymers are very attractive as porogens for the preparation of ordered mesoporous thin films and powders with pore sizes ranging from 40 down to a few nanometers in diameter because they are capable of both forming different superstructures and interacting with sol-gel precursors. In the present work, we report for the first time the synthesis of a series of highly crystalline rare-earth iron garnet (RE 3 Fe 5 O 12 , RE = Y, Gd-Dy) thin films with cubic networks of interconnected pores averaging 17 nm in diameter through facile polymer templating of hydrated nitrate salts. Despite intricate crystallization pathways, e.g., Y 3 Fe 5 O 12 via Y 4 Fe 2 O 9 and h-YFeO 3 , the nanoscale architecture of all these materials is only affected to a limited extent by solid-solid conversions at elevated temperatures.We specifically focus on the characterization of the morphology, microstructure and magnetic properties of polymer-templated Y 3 Fe 5 O 12 . This novel mesoporous material is single phase after heating to 900 °C, free of major structural defects and is also well-defined on the atomic level, as evidenced by a combination of in situ and ex situ scattering/diffraction techniques, electron microscopy, Raman and X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. The high quality of the nanocrystalline Y 3 Fe 5 O 12 thin films with overall soft magnetic-like characteristics and moderate anisotropy is further confirmed by SQUID magnetometry measurements. The magnetization behavior in the temperature range 5-380 K well describes Bloch's T 3/2 law for a 3D Heisenberg-type ferromagnet.

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Section: Resultsmentioning

confidence: 99%

Room Temperature Magnetic Rare-Earth Iron Garnet Thin Films with Ordered Mesoporous Structure

et al. 2013

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“…An energy level diagram is sketched in Fig. 4, the ordering of the states follows Larsen and Metselaar [13]. The exchange interactions are Jad = -39.8 K, Jdd = -13.4 K, and Jaa = -3.8 K.…”

Section: Fe3 O4mentioning

confidence: 95%

Conductivity and Magnetism of Magnetic Oxides

Gehring

2000

Acta Phys. Pol. A

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In a stoichiometric oxide the energy for the magnetic ordering is due to superexchange. This depends on the virtual transfer of a d electron from the transition ion to the neighbouring oxygen. When the oxide is p-doped there are compensating holes on the oxygen or the transition ion becomes mixed valent. The oxide may then conduct. The same transfer integral enters both the expression for the antiferromagnetic superexchange and the band width of the mobile carriers. Thus materials with a large antiferromagnetic exchange energy will be expected to have a relatively wide conduction band in the doped state and hence to have a high conductivity. In this paper the difference is explored between the materials in which there is true antiferromagnetism and those which are ferrimagnetic. In the antiferromagnets the carriers must destroy the magnetic order as they move. This behaviour is well known from the cuprates. In ferrimagnets the carriers may be able to move entirely on one sublattice. This occurs in Fe3O4 and probably in the doped garnets. In the case where motion is on one sublattice then doping does not destroy the magnetism and there is a relatively small magnetoresistance. An interesting feature is that unlike the cuprates the ferrimagnets do not become good metals at any doping but exhibit hopping conductivity. We explain the apparent paradox that the best conductivity is actually observed in materials where the conduction is only allowed when the antiferromagnetism has been quenched and that the conductivity in ferrimagnets is low.

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“…( 1) O. denotes oxygen ions on a normal lattice site, V. are oxygen vacancies, e are electrons, O*(g) denotes gaseous oxygen molecules and the dots and dashes indicate positive and negative charges relative to the normal charge of the neutral lattice.…”

Section: O * Vo" + Me' + K 02(g)mentioning

confidence: 99%

Diffusion of oxygen vacancies in yttrium iron garnet investigated by dynamic conductivity measurements

Metselaar

Larsen

1976

Solid State Communications

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Abstract-In yttrium iron garnet, Y3Fe,0,,, the oxygen vacancy concentration at high temperatures depends on the partial oxygen pressure. Due to the electron donating nature of the vacancies, changes in the oxygen vacancy concentration can be measured by electrical conductivity measurements. We discuss a dynamic method for studying the diffusion of oxygen vacancies by measurements of the time dependence of the electrical conduction after a change in the oxygen partial pressure has taken place. It is shown that the interpretation of the measurements is straightforward if the relative change in conductivity remains small (6 10%). Measurements were performed on single crystals and on polycrystalline samples at temperatures !@O-1400°C. The samples were made n-type by substitution with Si or p-type by substitution with Ca, Zn or Pb. The partial oxygen pressure was changed between 1 and 0.1 atm. For all samples the diffusion coefficient D of the oxygen vacancies can be represented by D = A exp (-Q/RT), where A = tt400 cm%-' and Q = 2.90 eV. It is shown that the activation energy of 2.90 eV is due to the migration enthalpy of the vacancies only.

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Defects and the electronic properties of Y3Fe5O12

Cited by 43 publications

References 13 publications

Room Temperature Magnetic Rare-Earth Iron Garnet Thin Films with Ordered Mesoporous Structure

Room Temperature Magnetic Rare-Earth Iron Garnet Thin Films with Ordered Mesoporous Structure

Conductivity and Magnetism of Magnetic Oxides

Diffusion of oxygen vacancies in yttrium iron garnet investigated by dynamic conductivity measurements

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