The absorption spectra of Y₃Fe₅O₁₂ and Y₃Ga₅O₁₂:Fe³⁺ to 5.5 eV

Abstract

The absorption spectrum of Y3Fe,0,, (YIG) is obtained to 40000 cm-l and analysed by Gaussian fitting to the spectrum of &b' obtained from the absorption data and the known refractive index behaviour. The energies of the major components agree well with those obtained in Y3Ga,0,,:Fe3+. Comparison of the spectra of Y,Feo,o~Ga4.~10,, and YIG indicates that all transitions below 36000 cm-1 involve Fe3+ pairs and that the first charge transfer transition between the oxygen 2p band and the iron d-like bands occurs a t 35600 and 37400 cm-I in YIG and Y3Feo.ogGa4.g1O,, respectively with an oscillator strength of approximately 0.1. An assignment is forwarded for the pair bands in terms of intersublattice FeS+ charge transfer transitions with reasonable agreement between the expected and observed energies and intensities. An example of the use of the density of states plot, obtained from the analysis, to explain the features of impurity absorption spectra in YIG is given for YIG: Si.Es wird das Absorptionsspektrum von Y3Fe50,, (YIG) bis 40000 cm-I bestimmt und durch GauBsche Anpassnng an das Spektrum von analysiert, das aus den Absorptionswerten und dem bekannten Verhalten des Brechungsindex erhalten wurde. Die Energien der hauptsi-ichlichen Komponenten stimmen gut mit denen in Y3Ga30,,:Fe3+ tiberein. Ein Vergleich der Spektren von Y,Feo,ogGar,QlO,, und YIG zeigt, daI3 an allen Vbergiingen unterhalb 35000 cm-l Fe3+-Paare beteiligt sind und dal3 der erste Charge-Transfer-Vbergang zwischen dem Sauerstoff-2p-Band und dem Eisen-d-Band bei 35600 bzw. 37400 cm-l in YIG und Y3Feo,ogGa4,~10,, auftritt, mit einer Oszillatorstiirke von etwa 0.1. Eine Zuordnung der Paarbanden mit Inter-Untergitter-Fe3+-ChargeTransfer-Vbergiingen wird mit verniinftiger ubereinstimmung zwischen den erwarteten und beobachteten Energien und Intensitiiten vorgenommen. Ein Beispiel fur die Anwendung des aus der Analyse gewonnenen Zustandsdichtediagramms zur Erkliirung der Storstellenabsorptionsspektren in YIG wird fur Y1G:Si angegeben.

Nonlinear optical spectroscopy of epitaxial magnetic garnet films

“…Although the optical absorption and the magnitudes of the linear magneto-optical signals are very different in the three films, their third harmonic spectra are similar. The tetrahedral transition 6 1 4 2 A T ® centered near 2.4 eV is well resolved in the TH spectrum, and in particular in the YIG/GGG(111) film. Note that the strong increase of the linear absorption above 3 eV is not accompanied by a similar increase of the TH spectra.…”

“…In its middle part Fig. 1 shows experimentally observed transition energies in YIG as reported in several papers [5,6,[9][10][11][12][13][14][15]. The electronic structure of iron garnets has been a subject of calculations based on crystal field theory and molecular orbital theory [5,9,14,[16][17][18].…”

“…cm above 5 eV [6]. The linear magneto-optical properties of garnets, and in particular bismuth-substituted garnets, have attracted a lot of interest due to the fact that very high values of the specific Faraday rotation up to 10 5 deg/cm were observed at room temperature.…”

“…Below the band gap the electronic transitions could be studied by transmission methods based on optical and magneto-optical techniques, whereas for transitions above the band gap of » 3.2 eV reflection methods are in general more favorable [9,11,12]. With the use of very thin YIG films (t = = 0.26 mm) absorption spectra could be obtained up to 5.0 eV [6]. It should be noticed that all optical transitions between the localized states of the Fe 3+ ions are spin-forbidden.…”

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

“…[56] 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. [57][58][59] The optical band gap at room temperature was found to lie in the range 2.6 eV to 2.9 eV and has been shown to arise due to excitation from O 2p valence band to Fe oct 3d conduction band. [60][61][62] For this reason, YIG is referred to as a charge-transfer insulator.…”