Optical absorption of the Gd3Ga5O12 epitaxial films grown from Bi2O3-B2O3-CaO solution melt system

Single-crystalline garnet films with a stoichiometric composition of Gd₃Ga₅O₁₂ were grown for the first time by liquid phase epitaxy from a supercooled melt of the Bi₂O₃-B₂O₃-CaO solid solution system. The films exhibit no absorption bands in the visible spectral range.     

Control of the anisotropy field of successively grown garnet films

The anisotropy field of magnetic bubble garnet films grown by LPE is an important property to be controlled as well as the bubble collapse field and the strip width. The anisotropy field is comparatively likely to drift with run number even if the characteristic length can be kept constant and directly affects the device operation. In order to suppress the drift of the anisotropy field, the melt compositional drift must be suppressed by the periodic addition of garnet oxides and flux to the melt.     

Dislocations in Y3Al5O12

The energies of dislocations in yttrium aluminium garnet are calculated and the likely configurations of both growth and mechanically induced dislocations in crystals grown from solution and from the melt are discussed.     

Reproducible garnet film preparation using fast growth rates

Large numbers of uniform defect free magnetic garnet films having essentially identical properties can be prepared from the same melt using conventional LPE dipping techniques when growth rates of 2–4 μm/min are employed. Such fast growth rates suppress compositional drift in successive films and avoid second-phase precipitation. Data is given for 40 highly perfect films (> 1 cm², 4πM_S = ～ 200 gauss) grown sequentially from the same melt. Melt composition and growth conditions necessary to achieve fast growth are discussed.     

Microwave relaxation properties of Be2+-doped yttrium iron garnet LPE films

A series of yttrium iron garnet epitaxial films containing an increasing concentration of beryllium has been grown and studied by the FMR technique in the microwave range. A nearly linear increase of the films line-width with the BeO content in the melt together with high temperature air annealings and reduction treatments in aqueous solutions evidences the presence of Fe⁴⁺ Be²⁺ pairs in the lattice to provide ion charge equilibrium.     

Growth reproducibility of the bubble properties of (YSmLuCa)3 (FeGe)5 O12 films

Reproducibility of CaGe garnet films grown by LPE is discussed in comparison with that of Ga garnet films. The influence of growth temperature deviation on the properties of CaGe garnet films is not compensated by the adjustment of the substrate rotation rate, although it is effective for Ga garnet film growth. On the other hand, the bubble collapse field of CaGe garnet films is less sensitive to the growth temperature than that of Ga garnet films. Therefore by determining the growth time accurately the bubble collapse field of as-grown films has been controlled within ±1%, even if the growth temperature deviates from the desired value by ±1°C.     

Control of the properties of magnetic garnet films

Large numbers of magnetic garnet films having essentially identical properties can be prepared from the same melt using the conventional LPE dipping technique, in which substrate rotation rate is adjusted to compensate for the difference between the growth temperature and the objective, thereby the growth rate can be completely controlled. Melt compositional drift has been suppressed by the periodic addition of garnet oxides and flux to the melt.     

Epitaxially grown Bi-substituted iron garnet films for magneto-optic devices

The growth conditions and magnetooptical properties of films of Bi-substituted iron garnets are described. The chemical composition of TmBiFe-Ga garnet films grown from a PbO,B2O3flux has been determined using the radiotracer technique of chemical analysis. The maximum value of the figure of merit (Faraday rotation per unit optical attenuation) found for these films is 2.5 deg/dB at 560 nm. Annealing experiments show that the lead incorporated in these films does not appreciably influence the optical absorption. Using a flux of Bi2O3,MeO2(with Me = Si,Ce), Bi-substituted iron garnet films have been grown. For (TmBiFeGa) garnet films a value of the figure of merit of 3.5 deg/dB at 560 nm is obtained. The Faraday rotation and the optical absorption are measured in the visible for (YBiFeGa)8O12films grown on a large lattice constant substrate. The figure of merit at 560 nm was found to be 4.7 deg/dB.     

Epitaxial growth and annealing control of FMR properties of thick homogeneous Ga substituted yttrium iron garnet films

Homogeneous, 30 μm to 70 μm thick Ga substituted yttrium iron garnet films have been grown on Y or Al substituted gadolinium gallium garnet substrates having lattice parameters matched to that of the films. Resonance field and FMR linewidth measurements as a function of frequency and annealing experiments revealed that the magnetization and cubic anisotropy of the films are identical to data from flux grown bulk single crystals, the FMR losses of the films are only slightly higher. For films grown with supercooling ΔT < 50 °C a negative, growth induced, uniaxial anisotropy was found which could be removed by annealing in air at 1100 °C. A compensation of the temperature drift of the FMR frequency can be adjusted in the Ga substituted films by changing the frozen-in Ga-Fe cation distribution by annealing and quenching from different temperatures > 800 °C.     

LPE growth reproducibility of garnet bubble materials

The problem of growth reproducibility in liquid phase epitaxy of bubble garnet films is analysed. Deviations of the optimum growth temperature are considered to be the main cause of non-reproducibility of the film properties. An expression is derived for the growth temperature sensitivity of the bubble collapse field of grown films. Evaluation of this expression shows that the sensitivity can be minimized if the growth temperature derivative of the magnetization can be adjusted in a controlled way, preferably in the range of 3 to 6 Gauss/°C. This derivative is determined for several melts of the usual CaGe:YIG-type. It is found to be almost independent of the melt composition and always larger than 5 Gauss/°C. Thus growth reproducibility can be improved to a rather limited extent for such CaGe:YIG-type melts.     

Optical absorption in cobalt-containing epitaxial films of gadolinium gallium garnet

The optical absorption of di-and trivalent cobalt ions embedded in single-crystalline films of gadolinium gallium garnet was observed in the samples grown by liquid-phase epitaxy from supercooled solution melts based on PbO-B₂O₃ and PbO-B₂O₃-GeO₂ systems.     

Calcium germanium substituted iron garnet films for magnetic bubble applications

Mixed rare earth iron garnet films containing calcium and germanium have been grown on (111) oriented gadolinium gallium garnet (GGG) substrates. The effect of growth conditions on film composition and properties is discussed. The 5 μm diameter bubble films have good magnetic properties; however, temperature control during film growth is very critical.     

Fractal Dimension Behaviour of Maze Domain Pattern in Ferrite-Garnet Films During Magnetisation Reversal

Journal of Superconductivity and Novel Magnetism - Experimental results of the study of magnetic bismuth-containing ferrite-garnet films grown on substrates from gadolinium-gallium garnet are...     

Growth and characterization of Al-substituted iron garnets for submicron diameter bubble films

Al-substituted rare-earth iron garnet films have been grown that support submicron diameter bubbles. In developing small diameter bubble films, reduction of the saturation induction of a film, 4πMS, is very important because power consumption in drive coils and chip heating increase drastically with higher magnetization. Aluminum ions have been found to be one of the most suitable substitution ions for this purpose. Moreover, owing to the small ionic radius of Al ions, it is easy to meet the lattice matching requirement between films and GGG substrates without lattice adjusting ions such as lutetium. Submicron diameter bubble films are easily grown by the conventional LPE technique in the garnet system (YSmGd)₃ (FeAl)₅ O₁₂. They show good bubble properties, well suited to practical use.     

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·B₂O₃ 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 Li₂MoO₄Y₂O₃MoO₃ pseudo-ternary system and solubility are discussed as related to crystal and film growth.     

The effect of substrate defects on epitaxial magnetic garnet films

The stress patterns associated with various defects in Czochralski-grown gadolinium gallium garnet (GGG) crystals have been observed using a polarizing microscope. The effect of these defects on both the surface topography and the magnetic behaviour of epitaxial magnetic garnet films grown on GGG substrates is reported. In particular, iridium inclusions and defects of a filamentary nature affect the surface topography. Other types of defect influence the magnetic behaviour of the films in a manner attributable to a change in the lattice parameter.     

Substrate facet replication by epitaxial magnetic garnet films

Epitaxial ferrimagnetic garnet films were deposited on Czochralski grown single crystal gadolinium gallium garnet substrates containing faceted regions. Films grown by both chemical vapor deposition (CVD) and liquid phase epitaxy (LPE) were studied. Lattice parameter distributions were determined by the method of X-ray double crystal topography with rocking curve analysis. The demagnetized domain strip width, magnetization, and characteristic length were measured in a CVD film in regions inside and outside the substrate facets. It was determined that replication of the substrate facets by the epitaxial film is accomplished by a difference in film stress. This stress difference arises from the lattice parameter difference between the faceted and unfaceted regions of the substrate. These results lead to the establishment of a criterion for allowable lattice parameter variation in substrates to be used for magnetic bubble domain films with stress induced anisotropy.     

石榴石型磁光存储材料

稀土铁石榴石薄膜被认为是最具应用前景的下一代磁光记录材料。稀土铁石榴石薄膜具有高的矫顽力、良好的热、化学稳定性及强的磁光效应等特点；特别是当Ｂｉ３＋和Ｃｅ３＋离子部分取代石榴石结构中的稀土离子后，可以极大地增强其磁光效应。本文就磁光记录的原理、磁光存储材料、稀土铁石榴石磁光薄膜的制备及其如何降低石榴石薄膜中的晶界噪声等问题作了一些探讨。     

Optical absorption in Gd3Ga5O12 epitaxial films grown from PbO-B2O3 based fluxed solution

We report the observation of additional optical absorption in single-crystal garnet films with the nominal composition Gd₃Ga₅O₁₂, grown by liquid-phase epitaxy from a supercooled fluxed solution based on PbO-B₂O₃. Pis’ma Zh. Tekh. Fiz. 25, 18–22 (September 12, 1999)     

Rare earth-yttrium iron-gallium garnet epitaxial films for magnetic bubble domain applications

(RE,Y)₃(Fe,Ga)₅O₁₂ garnets, where RE=Eu or Gd, have been developed for use as magnetic bubble domain materials. Magnetic and crystallographic studies were used to find suitable compositions for epitaxial thin films on nonmagnetic garnet substrate crystals. Properties of films grown by liquid phase epitaxy on Czochralski Gd-Ga garnet (111) substrates are discussed. Uniaxial anisotropy in the films can be interpreted as being the result of a lattice mismatch stress mechanism. The Gd-Y films with uniaxial anisotropy are in tension while the Eu-Y films are in compression as shown by lattice spacing differences between films and their substrates. Uncracked, high stability Eu-Y films with very high compressive stresses were grown. Annealing experiments reveal significant changes in anisotropy which correlate with large changes in film lattice spacing. Thus, it is possible to obtain high uniaxial anisotropy in garnets containing only one kind of rare earth ion together with a nonmagnetic ion such as yttrium. These films support domains with very high wall velocities at typical device drive fields.