Yttrium Gallium Garnet Research Articles

Photoluminescence of Cr 3+ ions in RF-sputtered YGG thin films

This paper reports measurement of the R-line and 4T 2→ 4A 2 emission spectra of Cr 3+ ions in RF-sputtered yttrium gallium garnet (YGG) thin films. The variation of the shape of the R-line and its vibronic sideband with composition of the YGG thin film is discussed.

Reflectivity in yttrium iron garnet between 4 and 30 eV using synchrotron radiation

The optical reflectivity at 300 K in yttrium iron garnet YIG between 4 and 30 eV was measured using synchrotron radiation spectroscopy. By means of the Kramers-Kronig analysis and with the aid of the results of previous reflectivity experiments the spectra of complex permittivity e′, e′ and of the optical constants (n, k) were obtained in the range from 2 to 30 eV. The results are compared with those published by Galuza et al. [Fiz. Tverd. Tela15 (1973) 585 and17 (1975) 2863]. A good agreement with their YIG spectra is found. However, by virtue of the continuous synchrotron radiation source the present spectra reveal more details and cover a broader spectral range. A close analogy between YIG and non-magnetic yttrium gallium garnet spectra is observed above 6 eV.

Czochralski crystal growth and aluminum segregation coefficient in yttrium gallium aluminum garnet

The aluminum distribution coefficient and the amount of octahedral yttrium aluminum gallium garnet single crystals obtained by the Czochralski method have been determined from lattice constant variations during crystal growth. The value of the aluminum distribution coefficient was close to 2 for those parts of the crystal with a convex solid-liquid interface and it was close to 1 for those with a flat 〈111〉 solid-liquid interface. The large difference between these values can be explained by chemical stresses in the crystal in the meltback region and small changes of the lattice constant in the part of crystal with a flat 〈111〉 solid-liquid interface. Single crystals of yttrium aluminum gallium garnet with a lattice constant appropriate for LPE film growth of yttrium gallium garnet have been grown.

Luminescence properties of Tb-activated yttrium gallium garnet phosphors

Comparison of luminescence properties between electron-excited and uv-excited yttrium gallium garnet: Tb phosphors is reported. Although the thermoluminescence and phosphorescence in both cases are quite alike once traps are filled, an apparent difference in the behavior of trap filling has been observed. Small addition of V 2O 3 to these phosphors revealed a unique effect on luminescence properties either with the electron excitation or with the uv excitation.

A novel non-Pb flux system for the preparation of yttrium and rare earth iron gallium and aluminum garnets

A flux composed of lithium and rare earth molybdates has been found to be an effective transfer medium for the preparation of yttrium and rare earth iron gallium and aluminum garnets. Magnetic bubble domain properties of epitaxial iron garnet films grown from the molybdate flux are easily controlled by virtue of the transfer process including dimensional control for submicron thick films. The properties of these films compare well to those grown from the PbO·B 2O 3 flux, but the films are contaminant free. This is particularly important for the growth of Nd-doped YAG laser films. Stability region of the garnet phase in the Li 2MoO 4Y 2O 3MoO 3 pseudo-ternary system and solubility are discussed as related to crystal and film growth.

Fluorescence and absorption spectra of Tb 3+ ions in yttrium-gallium garnet

The data on the fluorescence and absorption spectra of the Tb 3+ ions in yttrium-gallium garnet in the region 3800–6800 Å have been obtained at 4.2 K and 77 K. The groups of fluorescence lines in the regions 3800–4830 Å and 4860–6800 Å have been assigned to transitions from 5D 3 and 5D 4, respectively, to the Stark components of 7F states. The analysis of the spectra led to the identification of six Stark components each for the 5D 3 and 5D 4 states and thirty-six components of 7F states. The local symmetry arround the Tb 3+ ions is found to be orthorhombic, in accordance with the complete removal of the degeneracy of the 7F 5 and 7F 1 electronic states.

Uniaxial stress dependence of the EPR spectrum of Ir4+ in Y3Ga5012

AbstractMeasurements have been made by EPR techniques of the stress dependence of the lowest Ir4+ (5d5; 2Ta2g) levels in yttrium gallium garnet. The results confirm the comparable behaviour of Ir4+ arid Ru3+ (4d5; 2T2g) ions at the octahedral sites in garnets in contrast to recent results obtained by ferrimagnetic resonance. On a simple molecular field model the Ir4+ energy levels in YIG: Ir4+ introduce a negative contribution to λ100and a smaller positive contribution to.λ111.

Optical properties of epitaxial iron garnet thin films

Optical absorption, derivative absorption, reflectivity, and derivative reflectivity data are presented for several iron garnet thin-film compositions grown by liquid-phase epitaxy. In the case of yttrium iron garnet (YIG), the real and imaginary parts of the dielectric response function $\ensuremath{\epsilon}={\ensuremath{\epsilon}}_{1}+i{\ensuremath{\epsilon}}_{2}$ are compared with previously published results for bulk crystals and shown to be substantially larger. Based on absorption and reflectivity data for iron garnet films in which the tetrahedral and octahedral iron sublattices have been selectively diluted with gallium or scandium as well as measured absorption data for bulk crystals of yttrium gallium garnet dilutely doped with ${\mathrm{Fe}}^{3+}$, we propose an Adler-Feinleib split-density-of-states diagram for YIG. The main results include a series of weak crystal-field transitions between 1.4 and 3.4 eV, a pair of much stronger transitions at 2.9 and 3.2 eV which we tentatively associate with excitons of the configuration $2{p}^{5}3{d}^{6}$, strong $2p\ensuremath{\rightarrow}3d$ charge transfer bands above 3.4 eV where the final states are probably itinerant-one-electron band states, and very strong semiconductor like $2p\ensuremath{\rightarrow}4s$ optical transitions above about 8 eV which make the major contributions to the low-frequency refractive index. Some of the above assignments are defended by comparing optical properties of YIG, NiO, and SrTi${\mathrm{O}}_{3}$.

Wavelength modulation spectroscopy of epitaxial iron garnet films

Derivative absorption and reflectance spectra are reported for epitaxially grown iron garnet films and compared with derivative absorption results for bulk yttrium gallium garnet dilutely doped with Fe 3+ Results are briefly discussed in terms of crystal field transitions, charge transfer excitons, and charge transfer bands all involving the iron 3d electrons.

Optical Properties ofHo3+Ions in Yttrium Gallium Garnet and Yttrium Iron Garnet

Optical absorption and emission spectra are used to determine the energy levels of the $^{5}I_{8}$ ground state and $^{5}I_{7}$ excited state of ${\mathrm{Ho}}^{3+}$ in diamagnetic yttrium gallium garnet (YGaG) and ferrimagnetic yttrium iron garnet (YIG). The results for YGaG are consistent with the ${D}_{2}$ site symmetry of the dodecahedral site in the garnet structure. Energy levels in YIG which are separated by site inequivalency are identified from spectra observed as the ${\mathrm{Fe}}^{3+}$ magnetization is rotated in the ($1\overline{1}0$) plane. Stimulated emission is observed from ${\mathrm{Ho}}^{3+}$ in YGaG at 2.086 and 2.114 \ensuremath{\mu} and from ${\mathrm{Ho}}^{3+}$ in YIG at 2.086, 2.089, and 2.107 \ensuremath{\mu}. Each of the lines in YIG is composed of two superimposed electronic transitions. The exchange field in YIG makes possible magnetic tuning of coherent emission over a range of 70 \AA{}.

Crystal field spectra of d3,7 ions. VI. The weak field formalism and covalency

When the problem of an ion in a crystal field is solved using the unperturbed atomic wave functions as basis functions, the free ion energies appear explicitly in the diagonal terms of the secular determinant where they can be adjusted as experimental parameters. By fitting the observed crystal field energy levels in this scheme, a set of modified free ion energy levels can be derived for Dq = 0, and it is found that in most cases a single set of electrostatic repulsion parameters F2 and F4 describes the energies, provided a Trees correction is applied. The values of F2 and F4 obtained in this way from crystal spectra of Cr3+ in ruby, yttrium gallium garnet, other oxides, and K3Cr(CN)6 and of Co2+ in ZnAl2O4 are reduced by covalency from their free ion values. The reduction for P2 is greater than for F4 because of its greater sensitivity to the outer part of the radial distribution function, where covalency plays its major part. It is concluded that the differential expansion of the t2 and e orbitals in the crystal field is not great, and that nephelauxetic effects in crystal field spectra should more properly be related to the F2 and F4 parameters of Condon and Shortley through the weak field formalism, rather than to Racah's B parameter in the strong field approach. The latter results in unsound conclusions about the effects of covalency. Analysis of the spectra of CrBrs and C0C14" suggests that the d electrons are not adequately described by two electrostatic repulsion parameters and the usual crystal field theory should be applied cautiously.

Crystal Field in Dysprosium Garnets

The crystal-field splittings of the $^{6}H$ and $^{6}F$ multiplets of ${\mathrm{Dy}}^{3+}$ in yttrium gallium garnet and yttrium aluminum garnet have been determined from absorption and emission spectra. In addition, the $g$ factors of some crystal-field levels have been determined from Zeeman-effect measurements. All these experimental data are used to derive a set of crystal-field parameters for the two garnet systems. In these calculations, the full Hamiltonian appropriate for the ${D}_{2}$ symmetry at the rare-earth sites and also the mixing of the different $J$ states by the crystal field were taken into account. The agreement between experimental results and calculations is very satisfactory, and of the same quality as for the case of ${\mathrm{Yb}}^{3+}$, where far fewer experimental results had to be fitted.

Optical transitions in Tm 3+ doped Y 3Ga 5O 12 near 2.0μ

The photoluminescence spectrum of Tm 3+ in yttrium gallium garnet is presented, and is shown to demonstrate the operation of selection rules.

Thermal expansion of yttrium and gadolinium iron, gallium and aluminum garnets

Lattice constants of yttrium and gadolinium iron and gallium garnets and of yttrium aluminium garnet have been measured in the temperature range 296–1400°K. The results show that among these, GdGaG gives the closest match of Δa/a0 vs. T to YIG and to GdIG.

A Zeeman-Raman experiment

Electronic Raman scattering to crystal field levels of the 2F 7 2 manifold of a single crystal of ytterbium in yttrium gallium garnet placed in magnetic fields up to 48 kG has been observed. The electronic levels of one of the crystal field states has been found to be extremely sensitive to the effect of the external field which is at least to a first approximation in agreement with a crystal field analysis.

Magnetic Behavior of Cobalt in Garnets. I. Spin Resonance in Cobalt-Doped Yttrium Gallium Garnet

We have studied the spin resonance at 24 and 56 kMc/sec of cobalt in single crystals of yttrium gallium garnet (YGaG). We find resonances associated with four different combinations of site and charge state. Tetrahedral ${\mathrm{Co}}^{2+}$ has the $^{4}A_{2}$ ground term with the tetragonal splitting parameter $2D=\ensuremath{-}36$ ${\mathrm{cm}}^{\ensuremath{-}1}$. Octahedral ${\mathrm{Co}}^{2+}$ has the $^{4}T_{1}$ ground term with the trigonal splitting ${\ensuremath{\Delta}}_{t}=+650$ ${\mathrm{cm}}^{\ensuremath{-}1}$. It is seen in otherwise pure YGaG, as well as in crystals counterdoped with ${\mathrm{Si}}^{4+}$. Tetrahedral ${\mathrm{Co}}^{3+}$ has the $^{5}E$ ground term, with $D\ensuremath{\sim}14$ ${\mathrm{cm}}^{\ensuremath{-}1}$, $|a|=0.66$ ${\mathrm{cm}}^{\ensuremath{-}1}$. This value of $a$, the fourth-order cubic field-splitting parameter, is exceptionally large and makes possible strong magnetic-dipole transitions between states with ${S}_{z}=\ifmmode\pm\else\textpm\fi{}2$. Electric-dipole transitions are also observed between these states. Octahedral ${\mathrm{Co}}^{4+}$ has the strong-field $^{2}T_{2}$ ground term, with ${\ensuremath{\Delta}}_{t}=+1000$ ${\mathrm{cm}}^{\ensuremath{-}1}$; its spectrum is very weak relative to ${\mathrm{Co}}^{3+}$, even in crystals counterdoped with ${\mathrm{Ca}}^{2+}$. The absence of a resonance from octahedral ${\mathrm{Co}}^{3+}$ implies that this ion has the strong-field $^{1}A_{1}$ ground term. Cobalt does not appear to enter the dodecahedral site in our crystals. Our results are complementary to, and on the whole consistent with, the optical data of Wood and Remeika. We review the information available on crystal fields at the octahedral and tetrahedral sites in garnet, and on the hyperfine structure of cobalt.

Optical Studies of Ho3+ Ions in YGaG and YIG

Optical absorption and emission spectra are used to determine the energy levels of the 5I8 ground state and 5I7 excited state of Ho3+ in diamagnetic yttrium gallium garnet (YGaG) and ferrimagnetic yttrium iron garnet (YIG). The results for YGaG are consistent with the D2 site symmetry of the dodecahedral site in the garnet structure. Energy levels in YIG that are separated by site inequivalency are identified from spectra observed as the Fe3+ magnetization is rotated in the (11̄0) plane. Stimulated emission is observed from Ho3+ in YGaG at 2.086 and 2.114 μ and from Ho3+ in YIG at 2.086, 2.089, and 2.107 μ. Each of the lines in YIG is composed of two superimposed electronic transitions. The exchange field in YIG makes possible magnetic tuning of coherent emission over a range of 70 Å. This paper is a brief description of work that will be treated in full elsewhere.

Crystal Field in Samarium and Dysprosium Garnets

The crystal-field energy levels of the 6H and 6F multiplets of Sm3+ and Dy3+ in yttrium aluminium (YAG) and yttrium gallium garnet (YGG) have been fitted to the Hamiltonian appropriate for the D2 site symmetry of the rare earth ion. A good fit has been obtained for both garnets. For the dysprosium garnets also the groundstate g factors were found to agree well with the calculated ones.

Note concerning the spectra of rare earth ions in garnets

Experimental evidence is presented which shows the operation of selection roles in the non-Kramer's ion Tm 3+ in yttrium gallium garnet. No previous spectral analysis of any non-Kramer's rare earth ion in the garnet has considered selection rules, therefore all previous crystalline field calculations made from the spectra of non-Kramer's rare earth ions in garnets are meaningless.

Photoelastic Constants of Selected Ultrasonic Delay-Line Crystals

All of the photoelastic constants of cubic SrTiO3, yttrium gallium garnet, and sapphire, three of the constants of LiNbO3, and all except p44 of rutile have been measured relative to those of fused quartz. The measurements were made at room temperature using 6328 Å light. The photoelastic tensor of sapphire is unusual because all of the off-diagonal components appear to be very small or zero.