GGG Substrates Research Articles

ChemInform Abstract: Growth of BCSCO Single Crystals by a Slow‐Cooling Flux Method

Abstract(BCSCO: Bi‐Ca‐Sr‐Cu‐O).

DETERMINATION OF THE ANISOTROPY CONSTANTS Ku AND K1 OF GARNET BUBBLE FILMS BY MEASURING TORQUE CURVES

The dependence of the magnetic torque of single crystal GGG (Gd3Ga5O12) substrates on their geometry and some related physical parameters were studied. A method was proposed to deduce the substrate contribution in determining the uniaxial anisotropy constant Ku and magnetocrystalline one K1. Both Ku and K1 can be acquired from the magnetic torque curves by employing the two-variable regression and using computer. As example, the measured curves of Ku and K1 as a function of temperature were presented.

Crystal Growth of InP on a Gd3Ga5O12 Substrate by Organometallic Chemical Vapor Deposition

This paper reports the results of crystal growth of InP on a Gd3Ga5O12 (GGG) substrate. Effectiveness of the In-P/GaInAsP superlattice is shown. Substrate orientations of (100) and (111) are compared. By using the GGG(100) substrate and introducing the superlattice, the best result was obtained for growing an InP layer. From X-ray diffraction analysis, it was found that the grown InP layer was preferentially (111) oriented along the film normal. SEM and RHEED observation revealed that the grown layer was composed of polycrystalline grains with random orientation in the film plane.

Microstrip lines using yttrium iron garnet film

The spectral-domain technique is used to compute the dispersion characteristics and the transverse field distributions of microstrip lines using a yttrium-iron-garnet (YIG) film on a gadolinium-gallium-garnet (GGG) substrate. Numerical results are presented to show a sharp cutoff characteristic for a large thickness of GGG (which is caused by the reduction in the negative permeability range), and to show the effect of YIG film thickness on the nonreciprocal behavior. Experiments are carried out using YIG film a few tenths of a micrometer thick and a 400- mu m-thick GGG substrate. A narrow stopband characteristic of 200 MHz is observed at 6 GHz, which agrees well with theory. The application to a band-rejection filter is briefly discussed. >

Growth of BCSCO single crystals by a slow-cooling flux method

Single crystals of bismuth-calcium-strontium-copper-oxygen (BCSCO) were grown using a conventional slow-cooling flux method using KCl as a solvent. BCSCO single crystals having a surface area of about 10 mm 2 were also grown by the slow-cooling method from a 4334 BCSCO melt. The composition of the thin plate-like BCSCO crystals was determined by electron beam X-ray microanalysis. Susceptibility measurements of the as-grown crystals showed the extrapolated T c at 87 K. Polycrystalline layers up to 16 μm thickness deposited on GGG substrates from KC1 flux showed superconductivity below 85 K. According to our results this flux can be used for epitaxial growth of BCSCO superconductors.

Garnet films for 64 Mb bubble memory devices

Garnet films of (BiSmLu)/sub 3/(FeAl)/sub 5/O/sub 12/ supporting 0.4-0.45- mu m diameter bubbles have been studied for use in 64-Mb bubble memory devices. Using CaMgZr:GGG substrates with a large lattice constant (12.498 AA), the anisotropy energy K/sub u/ can be increased to 2.5*10/sup 5/ erg/cm/sup 3/ by increasing the Sm content in the film. Consequently, the bubble diameter can be reduced to 0.4-0.45 mu m, keeping the effective anisotropy field (H/sub k/-4 pi M/sub s/) at more than 1500 Oe. For the films on GGG with a K/sub u/ value of about 1.8-10/sup 5/ erg/cm/sup 3/, the value of H/sub k/ and/or the film thickness must be decreased compared to the values for films on CaMgZr:GGG in order to reduce the bubble diameter to less than 0.45 mu m.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Paramagnetic resonance losses in GGG (Gd3Ga5O12) substrates

Paramagnetic resonance losses in GGG (Gd3Ga5O12) substrates

Ce置換 YIG LPE膜のファラデー効果

Cerium-substituted YIG (YCeIG) films were grown on (111) oriented GGG substrates from PbO/B2O3 = based fluxes using the liquid phase epitaxy method. R5 parameter value about ten times as large as the usual one was used to increase the amount of the cerium entering the crystal. The Faraday rotation spectra were measured in the visible region (0.5～0.9μm) at room temperature. It was found that the Faraday rotation increased in the region between 0.65 and 0.85μm due to the cerium ion incorporated into the garnet films.

Microstructure of sputtered garnet films for magneto-optical recording media

Sputtered garnet films have a high potential for use as a magneto-optical recording medium. However, the medium noise is thought to be large because of its crystal boundaries. We investigated the microstructure of films on GGG substrate, using TEM and SEM. The film crystallized by postannealing shows a rectangular hysteresis loop with high coercivity, and has an uneven surface. This is because the direction and size of each crystallite is not uniform. However, the film crystallized during deposition has quite a smooth surface, but does not have magnetic properties suitable for use in magneto-optical recording. This film has a mosaiclike structure, in which all crystallites are uniformly oriented. We found that ion implantation of Ne+ and successive annealing of the film crystallized during deposition improved the magnetic properties without roughening the surface.

Read/Write Characteristics of Sputtered Garnet Optical Disks

The read/write characteristics of sputtered garnet magneto-optical disks are described. Polycrystaline films are grown on a glass substrate. In majority of the noise was found to come from the grain boundary. A good film was obtained under optimal sputtering conditions, with a carrier to noise ratio (CNR) of 45 dB. On a GGG substrate, an epitaxial film was obtained. Its CNR was 52 dB. No great improvement over a glass substrate was obtained. It seems that crystal defects are the cause of the noise.

Unidirectional properties of (YCa)&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;(FeCoGe)&amp;lt;inf&amp;gt;5&amp;lt;/inf&amp;gt;O&amp;lt;inf&amp;gt;12&amp;lt;/inf&amp;gt;films

The magnetic domain structure in (YCa) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (FeCoGe) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> films grown on {100} GGG substrates was investigated at room temperature. These films show unexpected low domain wall motion. Some unidirectional properties (eg. relaxation time, domain structure vanishing field) of the samples have been reported in this work. These properties can be changed using an external magnetic field.

Growth induced magnetic anisotropy in Co-doped garnet and its capability of application to magneto-optical memory materials

Growth-induced magnetic anisotropy (Kug) normal to the film surface in Co-doped iron garnet films grown on GGG substrates by the LPE method has been quantitatively discussed. Kug is increased with increasing Co content and growth rate (Vg). From the measurement of temperature dependence of magnetocrystalline anisotropy K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> , the parameter αλ is evaluated to be 80 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> through a curve fitting procedure using Slonczewski's theory of Co single-ion model for the anisotropy. After the annealing at temperatures above 900°C, Kug is disappeared and K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> is increased: These changes are successfully interpreted by the theory using the above value αλ. Also shown is the magnetic field effect on the perpendicular anisotropy of poly-crystalline Co-doped BiDyGeIG films prepared by the pyrolysis method on glass substrates for the purpose of application to magneto-optical memory materials. In these films, (Ge(CH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> COOH) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> is found to be a suitable solute for adding tetravalent Ge ions. In this method, an increase of Co amount raises the crystallization temperature, while doping of Ge lowers it. A magnetic field perpendicularly applied to the film during the heat treatment for crystallization enhances the anisotropy, whereby Ku is increased to about 170% of those of films prepared with no field.

Effect of Selective Tilt for GGG (111) Substrate Surface on the Magnetic Domain in Bubble Garnet LPE Layers

GGG (111) substrate surfaces are selectively tilted in an attempt to locally stabilize stripe domains. This method utilizes the magnetization easy axis inclination away from [111] in the tilted section. When an in-plane magnetic field (H r ) is applied to the substrate surfaces in a direction traversing the tilted section, a magnetic field is simultaneously produced in the magnetization easy axis direction of the tilted section. When an external bias magnetic field (H z ) is applied in the [111] direction, the effective magnetic field parallel to the magnetization in the tilted section can be modulated by H r . The results of our experiments demonstrate that this method can be used to simultaneously stabilize both the stripe domains of the tilted sections and the bubbles of the untilted regions at given H z .

Cobalt-titanium substituted barium ferrite films for magneto-optical memory

We have studied Faraday rotation and magnetic properties of Co-Ti substituted barium ferrite films with perpendicular anisotropy, which were prepared by targets-facing-type sputtering method on (111) oriented GGG substrates. Faraday rotation (θF) of 500–830 nm was measured by using the Faraday modulation method. It was found that θF increased proportionally to the content of cobalt in the wavelength range 700–830 nm. In the BaFe10.42Co0.78Ti0.8O19 film, Faraday rotation and magnetic properties were as follows: θF=0.75 deg/μm at 780 nm, anisotropy field: Hk=5.2 kOe, coercive force: Hc=800 Oe, Curie temperature: TC=380 °C. Thermomagnetic recording was achieved on this film by using a 780-nm laser diode. As a result, 2.0-μm bit patterns were observed by Faraday effect.

Magnetic Characteristics of Fine Permalloy Patterns

The magnetization behavior of patterned Permalloy film used in bubble memory elements is described. A total of 4.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> pattern elements were formed in Permalloy film evaporated onto a GGG substrate, spaced at a period of 4.5 μm. In-plane magnetization curves showed almost no change when a bias field was applied normal to the film, and patterning resulted in a strong shape effect. The in-plane magnetization curves had bends which were attributed to different magnetization characteristics prevailing in different portions of each pattern.

Integration of Garnet Films by Using Laser Etching Techniques

A new four-stage technique for integrating multiple iron garnet films on a single substrate is presented. A film is first grown on a GGG substrate by LPE. Ar ion laser etching is used in the second stage to remove a section of this film. Etching terminates automatically at the film-substrate interface. A second film is grown following the contours of the first by hetero-epitaxy in the third stage. The resulting film is flattened in the final stage by laser etching with the substrate and layered film immersed in phosphoric acid. This technique seems promising for realizing a wide variety of highly functional and compact integrated garnet film devices.

Growth-Induced Birefringence of Bi-Substituted Iron Garnet Films

Investigations into the relation between the growth-induced birefringence (?n f G) and Bi content in Bi garnet films are discussed. BiYMIG (M = Ga, A1) and YIG films were grown by the usual LPE method on {111}GGG substrates. Films with different Bi contents were grown by adjusting the R 2 (= Fe 2 O 3 /M 2 O 3 ) and Rs (= PbO/Bi 2 O 3 ) parameters and the growth temperature (T G = 800 to 900°C). The growth- induced birefringence ?n f G was obtained by analyzing the dependence of TE-TM conversion efficiency on the light propagation distance. In contrast to ? F , ? n fG does not depend on the amount of Ga or A1 present. The conclusion was that growth-induced birefringence in this system was due to the inhomogeneous distribution of Bi in the dodecahedral sites.

Magneto¿Opticial Properties of Bi¿Substituted GdIG Films Grown by LPE

Reduction of optical absorption as the amount of Bi in Bi-substituted films is increased is discussed. The amount of Bi in the films grown was controlled by adjusting the supercooling temperature of the solvent, the ratio of PbO to Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> in the solvent, the substrate rotation speed and other parameters. Variation in Bi content with respect to Bi-YIG was found at substrate rotation speeds of 84 rpm and 170 rpm. The measurements of the absorption characteristics of Bi-GdIG and Bi-GdGaIG films grown on a GGG substrate indicated that they included a Bi quantity of approximately 0.8 with respect to the Bi-GdIG. A figure of merit of 6.7 deg/dB was obtained for a 21.2 μm thick Bi-GdIG film at a wavelength of 0.76 μm.

RF-SPUTTER EPITAXY OF HIGHLY Bi-SUBSTITUTED GARNET FILMS FOR MAGNETO-OPTICAL APPLICATIONS

We have achieved in situ epitaxial growth of Bi2R1Fe3, 8Al1.2O12 (R=Y, Dy, Tb) films and Bi2Y1Fe5-2xCoxGexO12 (x=0, 0.5, 0.8) films on NGG and GGG substrates by rf diode sputtering at low temperature of 380°C. The epitaxy was as excellent as in LPE, when lattice mismatch was less than 0.5%. The Bi, Al : RIG films with good epitaxy were characterized by well defined and smooth magnetic domains and quite low coercive force of several Oe. The Co-substituted films had large magnetic anisotropy normal to the film plane as well as strong coercivity (∼0.1-1.2 kOe), which is ascribed to CO2+ ion located on octahedral sites. The magnetic anisotropy of these films was explained in terms of stress induced to the film.

Optical Magnetic Field Sensors Using Mixed Rare-Earth Iron Garnet Crystals

Optical magnetic field (current) sensors have recently reached practical application. This paper reports on evaluations of LPE garnet (TbY) IG crystals for magnetic field sensors, and on their optical characteristics. 100 ?m thick films were produced on {111} GGG substrate, but pits appeared even when using a Pb o /B 2 O 3 melt with a low 6.0 molar ratio. We studied the sensitivity and linearity of the Faraday rotation of these LPE films.