GGG Substrates Research Articles

Growth of magneto-optic Ce:YIG thin films on amorphous silica substrates

Abstract This paper presents a method for the growth of thin films of cerium substituted YIG (Ce:YIG) on an amorphous substrate. The Ce:YIG film was grown in two steps. The first step was the deposition of an amorphous film of CeY2Fe5O12 on a SiO2 substrate by RF-magnetron sputtering. The second step was crystallizing the film by raising its temperature to around 600°C in vacuum. A film of crysatllized Ce:YIG was obtained after this thermal treatment. For the thermal treatment process to work, a small chip of GGG plate was placed on the film. On the other hand, crystallization did not occur when the GGG chip was not placed on the film. The Faraday rotation θF was about 2300 deg/mm for light at a wavelength of 630 nm, and this was approximately the same value as for an epitaxial film of Ce:YIG on a GGG substrate. This method will be useful in the development of non-reciprocal planar light-wave circuits.

Single-crystal YIG phase shifter using composite stripline structure at X band

A tunable phase shifter at X band using single-crystal YIG film material grown on GGG substrates is fabricated. The phase shifter is a quarter wavelength in the absence of a bias magnetic field. The phase can be tuned 120° by varying the bias magnetic field from 3440 to 3720 Oe. The resultant variation in insertion loss was 0.5 dB. Measurements compared very well with calculations.

Imaging mechanisms of force detected FMR microscopy

We demonstrate spatial resolution of ferromagnetic resonance in a microscopic sample of YIG using ferromagnetic resonance force microscopy (FMRFM). Measurements were performed on a small single crystal YIG film grown on a GGG substrate, roughly rectangular in shape 20 μm×∼150 μm and 3 μm thick. The perpendicular and parallel force geometries of FMRFM, in conjunction with an external bias field both parallel and perpendicular to the film, were used to scan the sample. This enabled the detection of strong signals, even at atmospheric pressure and room temperature. The fundamental and higher-order magnetostatic modes were observed to have 26–29 Gauss separation. The intensity of these modes exhibited spatial variation as the magnetic tip was scanned over the sample, and this behavior is qualitatively explained by DE theory. An improved fabrication method for magnet on cantilever was employed, which yielded a spatial resolution of 15 μm. These results demonstrate the potential of FMRFM for investigating the spatial dependence of ferromagnetic resonance, and for studying the anisotropy fields and exchange coupling effects within multilayer films and small magnetic systems.

Selective-Area Growth of Magnetic Garnet Crystals by Liquid-Phase Epitaxy and Its Application to Waveguide Devices

Magnetic garnet layers with the composition of (LuNdBi)3(FeAl)5O12 have been grown on (111)-oriented Gd3Ga5O12 (GGG) substrates, which are patterned with stripes of different widths using a Ti mask, by liquid-phase epitaxy to fabricate one-step grown magnetic garnet waveguides. The garnet layers were investigated by scanning electron microscopy, X-ray diffraction measurements, energy-dispersive X-ray analysis and reflection high-energy electron diffraction. The layers grown on Ti-masked regions had a coarse and uneven surface, which is attributed to the damage in the surface of GGG substrates during the growth. The waveguiding experiment indicated that the light waves could be guided within the waveguide with a propagation loss of approximately 0.7 dB/mm.

Single-crystal yttrium iron garnet phase shifter at X band

A tunable phase shifter at X band using single-crystal yttrium iron garnet film material grown on GGG substrates is fabricated. The phase shifter is a fourth wavelength in the absence of a bias magnetic field. The phase can be tuned 120° by varying the bias magnetic field from 3440 to 3720 Oe. The resultant variation in insertion loss was 0.5 dB. Measurements compared very well with calculations.

Chemical composition, microstructure and magnetic characteristics of yttrium iron garnet (YIG, Ce:YIG) thin films grown by rf magnetron sputter techniques

YIG thin films were grown by rf magnetron sputter techniques. We investigated the effect of post-deposition heat-treatment as well as various deposition parameters such as substrate materials, substrate temperature, sputter power, and sputter gas types on the crystallinity, chemical composition, microstructure and magnetic characteristics of the films. Post-deposition heat-treatment over 750/spl deg/C was applied to crystallize as-prepared amorphous films, and a strong tendency of particular crystallographic planes lying parallel to substrate surface was observed for the heat-treated film on GGG substrate. The chemical composition of the film exhibited a wide range of chemical stoichiometry depending on the oxygen fraction of the sputter gas, and in particular the compositions of the YIG and Ce:YIG films deposited in sputter gas with an oxygen fraction of 20% were Y/sub 2.88/Fe/sub 3.84/O/sub 12/ and Ce/sub 0.24/Y/sub 1.10/Fe/sub 3.50/O/sub 12/, respectively. With raising the temperature of post-deposition heat-treatment from 900/spl deg/C to 1100/spl deg/C, the surface roughness of the film on GGG substrate increased, but coercive force as well as ferromagnetic resonance line width decreased.

Annealing behaviors of lattice misfit in YIG and La-doped YIG films grown on GGG substrates by LPE method

By the LPE method using the PbO–B 2O 3 flux system, YIG and La-doped YIG films were grown on GGG substrates. Lattice misfit and defect formation could be controlled by Pb ions which were incorporated into the garnet film. The lattice misfits of as-grown and annealed samples were investigated by double and triple crystal X-ray diffractometers. Films grew pseudomorphically regardless of stress types. When the film with high Pb content was annealed, the misfit and the FWHM of the rocking curve increased. It is supposed that the increase in misfit occurs as a result of the reduction of Pb 4+ to Pb 2+, which is compensated by the formation of oxygen vacancies. During heat treatment, PbO precipitates were formed in the film, which increased FWHM of the film. For the low Pb content films, no annealing-induced change occurred.

A novel flying magnetic readout head based on magneto-optic transfer

We have developed a novel flying magnetic readout Lead based on the concept of magneto-optical transfer. A special feature of this head is that its slider is made of a GGG substrate itself. To improve the readout characteristic of this head, the optical system was adjusted and the grooves were formed on a magnetic garnet film. The readout waveform and signal envelope became stable and the maximum CNR obtained was 52 dB (RBW=30 kHz). The CNR was almost constant for the recorded track width from 80 /spl mu/m to 2.7 /spl mu/m.

Non-equilibrium garnet films grown by pulsed laser deposition

Bi-substituted gadolinium iron garnet films were deposited on GGG(111) and NGG(111) substrates by irradiating KrF excimer laser on to targets with the composition Bi x Gd 3− x Fe 5O 12 (0≤ x≤3) at a substrate temperature of 580620 °C. Analyses on structure, composition and angle of Faraday rotation, θ F, were carried out. From these measurements, it is confirmed that a thermally non-equilibrium phase has grown when the amount of substituted bismuth, x, exceed 2.

LPE growth of yttrium–lutetium, indium–gallium garnet films for optical waveguide formation on a GGG substrate

Yttrium–lutetium, indium–gallium garnet single-crystal films with a composition of { Y x Lu 3−x}[ Y y1 Lu y2 In y3 Ga 2−y1−y2−y3]( Ga 3) O 12 (0⩽x⩽3, y1=0.02x, y2=0.12−0.04x, y3=1.08−0.11x) were grown on 〈1 1 1〉 - oriented GGG substrate by the LPE technique in order to fabricate a planar optical waveguide. The LPE growth results and optical properties of the films are reported. It was easy to control the composition of the film, because the distribution coefficients of the solutes showed gradual changes with the composition, and the coefficients ratios of Y/Lu and In/Ga, respectively, were 1.33–1.39 and 0.61–1.07. The films had high transparency in the visible and near-infrared regions. In this system, the addition of In increased and refractive index as a result of substitution on the Ga atom site. The films had a refractive index variation of ∼0.7% with the variation in the film composition, and this is large enough for optical waveguide fabrication. To evaluate its optical propagation loss as a waveguide material, a slab waveguide, composed of core and cladding layers, was formed on a GGG substrate. The propagation loss was 1.2 dB/cm at 1523 nm, indicating that the light was confined effectively in the waveguide with a low loss.

Actualités sur la maladie des agglutinines froides. À propos de cinq cas

This paper presents a method for the growth of thin films of cerium substituted YIG (Ce:YIG) on an amorphous substrate. The Ce:YIG film was grown in two steps. The first step was the deposition of an amorphous film of CeY2Fe5O12 on a SiO2 substrate by RF-magnetron sputtering. The second step was crystallizing the film by raising its temperature to around 600°C in vacuum. A film of crysatllized Ce:YIG was obtained after this thermal treatment. For the thermal treatment process to work, a small chip of GGG plate was placed on the film. On the other hand, crystallization did not occur when the GGG chip was not placed on the film. The Faraday rotation θF was about 2300 deg/mm for light at a wavelength of 630 nm, and this was approximately the same value as for an epitaxial film of Ce:YIG on a GGG substrate. This method will be useful in the development of non-reciprocal planar light-wave circuits.

FLYING HEAD FOR HARD DISK USING MAGNETIC GARNET FILM

We have developed a new type of flying readout magnetic head based on the concept of magnetooptical transfer ( MOT ) head. The slider of the head was made of a GGG substrate itself. Bi-substituted magnetic garnet film grown on the GGG substrate was used as a transfer readout layer. When 3.5 inch hard disk was rotated at a linear velocity of 10m/s, a carrier to noise ratio of more than 40dB was obtained for a recorded wavelength of 4 μ m.

Temperature dependence of the Faraday effect in Rh 4+-substituted magnetic garnets

The temperature dependence of the Faraday rotation (FR) spectra is measured for a single-crystalline (Y 3+,Ca 2+) 3(Fe 3+,Rh 4+) 5O 12 film grown by an LPE method onto GGG substrates at temperatures between 60 and 300 K in the wavelenght range of 0.7–1.6 μm. In addition, the FR spectra at some temperatures are calculated by a molecular-field approximation, and the calculated spectra are reproduced well by assuming the molecular field 155〈 S Z Fe〉 (cm −1), where 〈 S Z Fe〉 is a thermal average of an iron spin S Z Fe in magnetic garnets.

Laser Deposited Iron Garnet Films for Magneto-Optic Applications

AbstractSubmicron thick Bi, Ga substituted dysprosium iron garnet films were laser deposited on Gd3Ga5O12(GGG) and ceramic glass substrates at room temperature and then post annealed by rapid thermal annealing (RTA). From Faraday rotation studies, the films deposited on glass substrates are found to exhibit perpendicular magnetic anisotropy, Faraday rotation of 0.88 deg / μm, and coercive field Hc of 0.88 kOe. On the other hand, films deposited on GGG substrates with the same processing parameters are found to exhibit perpendicular anisotropy, but with much smaller values for Faraday rotation(0.03 deg; μm) and coercive field Hc(0.018 kOe). The uniaxial magnetic anisotropy with easy magnetization axis perpendicular to the film surface is caused by the stress induced on the polycrystalline film / substrate interface. The effect of changing the oxygen pressures, in the range of 20 to 100 mTorr during the deposition process, on the crystalline structure as well as coercive field and Faraday rotation angle are also presented.

Metalorganic Chemical Vapor Deposition of Magneto-Optical Ce:YIG Thin Films

AbstractThe deposition technologies of rare-earth substituted yttrium iron garnet (RE:YIG) thin films with a large Faraday rotation and their applications are briefly overviewed. Highly cerium substituted YIG films were successfully deposited on (111) GGG, (211) GGG, (100) MgO, and MgO buffered GaAs and InP substrates by single-liquid-source metalorganic chemical vapor deposition. Ce-YIG thin films can be epitaxially grown on lattice matched GGG substrates at a temperature as low as 600°C. They have excellent optical and magnetic properties along with high Faraday rotations. The films deposited on single crystal (100) MgO substrates are polycrystalline and have good magnetic properties. Sputter deposited MgO buffer layer was demonstrated for preventing the decomposition and chemical reaction of GaAs and LnP substrates resulting in successful deposition of YIG films on GaAs and InP substrates at a substrate temperature of 550°C. The films grown on MgO buffered GaAs substrates possessed good magnetic properties.

Characterisation of Pulsed Laser Deposited Bi Doped Dy Iron Garnet Thin Films on GGG(111), GGG(110), YSZ(100) and Si(100)

Bi and Ga substituted Dy iron garnet films (similar to 350 nm thick) have been pulsed laser deposited on single crystalline GGG (111), GGG (110), YSZ (100) and Si (100) substrates at a background pressure of 0.1 mbar and substrate temperature in the range of 550-590 degrees C. Epitaxial growth was obtained only in the case of GGG substrates. Growth on the other substrates resulted in randomly oriented polycrystalline layers. However, in all cases the films exhibited perpendicular anisotropy and Kerr blue spectra of comparable magnitude. The magnetic anisotropy was explained in terms of in plane tensile stress induced by the difference in thermal expansion coefficients between substrate and film. The magneto-optical (MO) behaviour in the 250-900 nm wavelength range, on the first three substrates was consistent with theoretical calculations based on the fundamental constants of BI:YIG thick films grown by LPE. MO studies for growth on Si suggested the presence of interfacial layers introduced by chemical reactions at the film/substrate interface.

Surface Morphology and Lattice Misfit in Yig and La: Yig Films Grown by Lpe Method on GGG Substrate

ABSTRACTY3Fe5O12(YIG) and La-doped YIG films were grown on the {111} GGG substrate using the PbO-B2O3 flux system. Pb, La incorporation and lattice misfit and annealing behaviors were studied. In the case of LPE growth of YIG film, lead ions from flux are substituted inevitably, and they play an important role in controlling film misfit. For a complete lattice matching, high supercooling is necessary in pure YIG growth, but this induces high defect concentration. In this experiment, La ions were added in the solution to sufficiently increase lattice parameter of the film grown under low supercooling. The concentration of substituted Pb and La were increased as the growth temperature was lowered and growth rate increased. The effective distribution coefficient of La was about 0.2 at a supercooling of 30 °C. The optimum growth conditions which bring about very small misfit were determined by measuring the misfit by double crystal diffractometer. Strain distributions of pre-annealed and annealed samples were investigated by triple crystal diffractometer.

Study of ultrathin Y3Fe5O12/Gd3Ga5O12 superlattices

High quality Y3Fe5O12/Gd3Ga5O12 (YIG/GGG) superlattices have been grown on (111)GGG substrates by pulsed laser deposition. The superlattices are investigated with the thickness of the YIG layer varied from six to one unit cells while keeping the GGG layer fixed at one unit cell. The thicknesses of the YIG and GGG layers are confirmed with grazing angle x-ray reflectivity (GAXR). The good quality of the samples is indicated by the small interface roughness, no more than 6 Å, also measured with GAXR. While the magnetization of the samples decreases when the thickness of the YIG layer is decreased, the superlattice remains magnetic even when the YIG layer is only one unit cell. Ferrimagnetic resonance indicates that there exists a surface anisotropy favoring in-plane magnetization.

FMR study of Co-substituted yttrium iron garnet films

Ferromagnetic resonance has been studied in Y 3− z Ca z Fe 5− x-y Co x Ge y O 12 films grown on the (001) plane of a GGG substrate. Temperature-induced spin-reorientation phase transitions were observed. On cooling the sample, the easy magnetization axes orientations changed from directions near [111] to [100], and the [001] direction had the lowest energy. The FMR signal was practically non-measurable below 60 and 120 K when the magnetic field was applied along the [110] and [100] axes, respectively.

Crystallinity of Ce Substituted YIG Films Prepared by RF Sputtering

The crystallinity of Ce-substituted yttrium iron garnet ( Ce1\\colonYIG) film was studied by measuring X-ray diffraction (XRD) and deformation and by transmission electron microscope (TEM) observation. The Ce1\\colonYIG films were prepared on anisotropic etched or unetched GGG and cation doped GGG (GCGMZG) substrates by RF sputtering. They have a narrow crystallization region as regards substrate temperature and this region becomes narrower as the O2 gas flow rate is increased. The XRD measurements and TEM observation revealed that crystallized Ce1\\colonYIG films have a multilayered structure except for those on GCGMZG substrates. Their layered structure was dependent on their thickness, the substrate treatment, the lattice constant difference between the film and the substrate and the O2 flow rate. They also exhibited compressive deformation which originated mainly from the lattice constant difference between the film and the substrate. The crystal growth mechanism of Ce1\\colonYIG films was considered on the basis of recent work on the growth mechanism of compressively deformed strained semiconductor film.