Takayuki Ishibashi

• Dr.
• Professor at Nagaoka University of Technology

Hexagonal and orthorhombic YMnO 3 thin films were prepared by metal-organic decomposition method, on (111) oriented yttria-stabilized zirconia (YSZ) and off-axis SrTiO 3 (001) substrates, respectively. Hexagonal YMnO 3 thin film on YSZ (111) substrate exhibit high crystallinity with (000l) orientation and an in-plane epitaxial relationships of YSZ...

Spatial light modulations (SLM) utilizing magneto-optical (MO) effect of magnetic materials are expected to offer fast switching and small pixel size as small as wavelength of the light. However, the small MO effect is a major issue. In this paper, we report a thermomagnetic recording of highly bismuth-substituted garnet film, known for large Farad...

A giant narrowing of the energy gap in the nonlinear optical crystal ZnGeP2 (ZGP) after the incorporation of manganese atoms into the chalcopyrite crystal lattice has been detected. The (Zn,Mn)GeP2 (ZMGP) thin films grown by solid-phase endotaxy on ZGP (001) substrate share the tetrahedrally coordinated structure of chalcopyrite. The measured fine...

----- Free to download link: https://authors.elsevier.com/a/1j8nn3IWkcEN%7Ey -----The first systematic study of linear and non-linear optical, magneto-optical and structural properties of pure TeO2 glass is presented with regard to different synthesis and material processing conditions. Prepared glasses were synthesized by the intermittent quenchin...

Free to download published version, Journal of Alloys and Compounds: https://authors.elsevier.com/a/1j8nn3IWkcEN%7Ey -----------The first systematic study of linear and non-linear optical, magneto-optical and structural properties of pure TeO 2 glass is presented with regard to different synthesis and material processing conditions. Prepared glasse...

The magneto-optical (MO) spectra of spinel cobalt ferrite thin films with different distortions were measured in a broad range of 0.59 – 3.54 eV. Instead of using the cation substitution method, we prepared cobalt ferrite thin films with local distortion by using a RF magnetron sputtering method on an Mg2SnO4 buffer layer to induce epitaxial strain...

Boron-induced electronic states of antiperovskite nitrides such as ferrimagnetic Mn 4 N were investigated via a combination of polar magneto-optical Kerr effect (p-MOKE) spectroscopy and spectroscopic ellipsometry (SE). The boron content in the Mn 4 N film varied from 0 to 4.3 at.%, for which the crystal structure was maintained. The amplitude of p...

Magneto-optical diffractive deep neural network (MO-D2NN) is a type of diffractive deep neural network that utilizes the magneto-optical (MO) effect of magnetic materials. MO-D2NN is composed of magnetic material, which is non-volatile and allows neurons to be rewritten. In our work, we fabricated and evaluated MO-D2NN with two layers containing $...

This paper provides a comprehensive review of magneto-optical (MO) spectroscopy. In the first place, different methods of MO measurements such as the Faraday effect, MO Kerr effect, and Cotton-Mouton effect are briefly introduced. Next, macroscopic and microscopic origin in magnetic materials is summarized. In the third part, measuring techniques f...

We propose a magneto-optical diffractive deep neural network (MO-D²NN). We simulated several MO-D²NNs, each of which consists of five hidden layers made of a magnetic material that contains 100 × 100 magnetic domains with a domain width of 1 µm and an interlayer distance of 0.7 mm. The networks demonstrate a classification accuracy of > 90% for the...

Hexagonal rare-earth manganese oxide YMnO 3 thin films were prepared on yttria stabilized zirconia (111) substrates by metal organic decomposition method. Crystallinity and morphology of YMnO 3 thin films crystallized at various temperatures were examined by X-ray diffraction and atomic force microscopy measurements, respectively. Single phase YMnO...

Bi-substituted rare-earth iron garnets, R 3− x Bi x Fe 5 O 12 (Bi:RIG), where R represents one of the rare-earth elements, exhibit the excellent magneto-optical (MO) properties that increase with Bi content x. In addition, magnetic properties of Bi:RIGs, such as the magnetization, the magnetic anisotropy, and the magnetostriction, could be controll...

The spin Hall effect, Dzyaloshinskii-Moriya interaction, Rashba effect, etc. are extremely important effects for the development of the conduction phenomenon of spin electronics due to the breaking of the spatial inversion symmetry of the hetero interface made of heavy metals such as Pt and W. These are due to SOI (spin-orbit interaction). Most of...

Magneto-optical (MO) imaging using MO imaging plates is a magnetic imaging technique that enables real-time measurements and is expected to be used for non-destructive testing and for observing the magnetic domains of magnetic materials. In this study, we propose a quantitative measurement method for three dimensional (3D) magnetic field vector mea...

Tunable microwave and millimeter wave oscillators and bandpass filters with ultra-low phase noise play a critical role in electronic devices, including wireless communication, microelectronics, and quantum computing. Magnetic materials, such as yttrium iron garnet (YIG), possess ultra-low phase noise and a ferromagnetic resonance tunable up to tens...

The Nd1Bi2Fe5O12/Nd2Bi1Fe4Ga1O12 polycrystalline films on the glass substrate and the Nd0.5Bi2.5Fe5O12 epitaxial films on the single-crystal gadolinium gallium garnet substrate have been investigated by impedance and dielectric spectroscopy. The inductive contribution to the impedance and two relaxation channels related to ferroelectric domains and...

Magneto-optical (MO) imaging using an MO material is one of the most important imaging techniques for measuring magnetic field distributions. The technique is attracting attention because of its ability to visualize magnetic fields and current distributions at a wide range of temperatures from cryogenic to room temperature or higher, a wide range o...

Pre-annealing process in the metal-organic decomposition (MOD) method for Bi-substituted Nd magnetic garnet films was studied. In this paper, we report on crystallinity and magneto-optical (MO) properties of Nd2BiFe4Ga1O12 and Nd0.5Bi2.5Fe5O12 thin films prepared with pre-annealing temperatures of 250 - 500ºC and annealing temperature of 650ºC. Dec...

Unlike ferromagnetic materials, ferrimagnetic metals have recently received considerable attention due to their bulk perpendicular magnetic anisotropy, low net magnetization and tunable magnetic properties. This makes them perfect candidates for the research of recently discovered spin-torque related phenomena. Among other ferrimagnetic metals, GdF...

In the conventional magneto-optical (MO) spectrometer, MO spectra are measured for each wavelength using the monochromatic light, resulted in a long measurement time more than 1 hour. To shorten the measurement time, we propose an MO spectrometer using a multi-channel spectrometer combined with the polarization modulation method, by which both Fara...

The mechanism of relaxation of the electric polarization in thin films of rare-earth-doped bismuth iron garnet on glass and gallium gadolinium garnet substrates is determined in magnetic fields of 0 and 12 kOe in the temperature range of 80–380 K. The change in the sign of the residual electric polarization after switching off the electric field an...

To prevent photocorrosion of a Cu2O photocathode, composition of a TiO2 layer onto the Cu2O is one of the most effective solutions. For crystallization of the TiO2 layer alone without heat‐damage to the underlying Cu2O layer, which is easy to oxidize to CuO, we developed the integration process of O2‐plasma and an excimer‐laser irradiation, that a...

To prevent photocorrosion of a Cu 2 O photocathode, composition of a TiO 2 layer onto the Cu 2 O is one of the most effective solutions. For crystallization of the TiO 2 layer alone without heat-damage to the underlying Cu 2 O layer which is easy to oxidize to CuO, we developed the integration process of O 2 -plasma and an excimer-laser irradiation...

We develop a light source, a polarizing film, and a highly bismuth-substituted neodymium iron garnet film which exhibits a large Faraday rotation angle of 11 deg., prepared on a 150 mm diameter glass substrate by the metal–organic decomposition method. To measure the magnetic field distribution quantitatively, the 45° polarizer method was carried o...

Magnetic properties of Nd3− xBi xFe5O12 (0 ≤ x ≤ 3) films prepared by metal organic decomposition on Gd3Ga5O12(100) substrates have been investigated. The Faraday rotation angle θF increased with bismuth concentration. The uniaxial anisotropy constant K u, cubic magnetocrystalline anisotropy constant K 1, gyromagnetic ratio γ, g-factor, and FMR lin...

In this work, polarization properties of the fifth harmonic signals of the scattered light in the apertureless-type scanning near-field optical microscopy (a-SNOM) were studied. SNOM images of a patterned Cr film were measured using Si probes having a tip radius of ~20 nm and a resonant frequency (Ω) of ~500 kHz. The polarization properties were me...

Electro- and magnetostriction mechanisms and temperature behavior of the length of bismuth-substituted neodymium iron garnet films on glass and gallium gadolinium garnet have been investigated. Electric- and magnetic-field and temperature dependences of the electro- and magnetostriction constants have been determined. It has been established that t...

We have prepared (11n) oriented Bi2Sr2CaCu2O8+x (Bi2212) thin films by metal-organic decomposition method. The vicinal (110) substrate of SrTiO3 (STO) inclined toward the [1¯10] direction was used for suppressing “c-twinning”. In the sample prepared in the O2 atmosphere, only the (11n) peak appeared in the θ-2θ X-ray diffraction pattern. When the m...

Thin films of the highly bismuth-substituted neodymium iron garnet Nd0.5Bi2.5Fe5-yGayO12 (Bi2.5Ga:NIG) were prepared on Nd2BiFe4GaO12 (Bi1Ga1:NIG) buffer layers on glass substrates. These thin films exhibited a large magneto-optical (MO) effect, demonstrating that the magnetic anisotropy of this material can be varied by substituting gallium for ir...

We numerically demonstrated that strong nanosized circularly polarized light (CPL) could be obtained using aperture antennas with three, four and five V-groove structures, due to the strong intensity enhancement effect of channel plasmon polaritons generated in the V-groove structures. Simulation results based on finite element method revealed that...

The rigorous coupled wave analysis is demonstrated by employing a recursive propagation algorithm based on an Airy-like internal reflection series, modified for a general cross-sectional distribution of permittivity. The method is capable of determining the electromagnetic field value at any point of the structure of any depth. Examples of simulati...

The magneto-optical (MO) imaging technique allows magnetic field distributions to be observed in real-time. In this paper, we demonstrate a MO color imaging technique that allows quantitative values of magnetic fields to be determined by the naked eye. MO color imaging is realized using a MO imaging plate, which contains a bismuth-substituted iron...

We investigated the optical and magnetic properties of a transparent magnetic garnet with a particular focus on its applications to atomic physics experiments. The garnet film used in this study was a magnetically soft material that was originally designed for a Faraday rotator at optical communication wavelengths in the near infrared region. The f...

We have developed a magneto-optical spatial light modulator (SLM) driven by spin-transfer-switching (STS), called spin-SLM, using a field-effect-transistor array active-matrix backplane, which plays an important role for developing large scale spin-SLM display devices. The fabricated spin-SLM device has 10 × 5 array pixel layout using magnetic tunn...

We have developed an active matrix-addressed magneto-optical spatial light modulator driven by spin-transfer switching (spin-SLM) which has a 100 × 100 array pixel layout with a 2 µm pixel pitch. It has pixel-selection-transistors and logic circuits which convert serial data into parallel data to reduce input terminals. We have confirmed successful...

In this work, we present a systematic study of optical and magneto-optical properties of Y3-xBixFe5O12 thin films with various Bi concentrations (x = 1.5, 2, 2.5, 3) prepared by Metal Organic Decomposition on Gd3Ga5O12 (100) substrates. We used magneto-optical spectroscopy and spectroscopic ellipsometry. Spectral dependence of complex refraction in...

Highly Bi-substituted neodymium iron gallium garnet thin films with a Bi content of 2.5, Nd0.5Bi2.5Fe5− yGa yO12 (NBIGG) with y = 0–1, on gadolinium gallium garnet (111) and (100) substrates have been prepared by metal–organic decomposition. Magnetic properties and magnetic anisotropy energies were measured using an alternating field gradient magne...

Optical and magneto-optical properties of amorphous Gd22Fe78 (GdFe) thin films prepared by direct current (DC) sputtering on thermally oxidized substrates were characterized by the combination of spectroscopic ellipsometry and magneto-optical spectroscopy in the photon energy range from 1.5 to 5.5 eV. Thin SiNx and Ru coatings were used to prevent...

We propose a magneto-optical (MO) color imaging technique that enables magnetic field distributions to be quantitatively observed in real-time. Values of magnetic fields are displayed as colors. MO imaging plates have been developed using highly bismuth-substituted neodymium iron garnet films, for use in MO color imaging. The films were prepared by...

This report presents a fundamental study on detecting ultrasonic waves utilizing near-field light. Scanning near-filed optical microscope (SNOM) is developed by modifying atomic force microscope (AFM). Obtaining AFM and SNOM images by changing probe-sample distance, the dependency of the distance for the intensity of scattered near-field light with...

We report on the preparation of (11n) oriented thin films of Bi2Sr2CaCu2O8+x (Bi2212), which were fabricated by the metal-organic decomposition method on SrTiO3 (110) and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. By controlling the post-deposition annealing condition (temperature 640 °C ≤ Ta ≤ 780...

Controlling magnetization of magneto-optical materials by voltage instead of electric current is expected to reduce power consumption and miniaturize functional elements in magneto-optical devices such as magneto-optical spatial light modulator. In this study, highly Bi-substituted neodymium iron gallium garnet, Nd0.5Bi2.5Fe4.5Ga0.5O12, thin film o...

Bi-substituted Neodymium Iron Garnet (Nd3-xBixFe5O12, Bi:NIG) thin films with the Bi composition x=0-1.0 are prepared on both the (001) and (111) oriented gadolinium gallium garnet (GGG) substrates by a metal organic decomposition method. Crystalline qualities and magnetic properties of these films are examined by X-ray diffraction, atomic force mi...

Polarization properties of apertureless-type scanning near-field optical microscopy (a-SNOM) were measured experimentally and were also analyzed using a finite-difference time-domain (FDTD) simulation. Our study reveals that the polarization properties in the a-SNOM are maintained and the a-SNOM works as a wave plate expressed by a Jones matrix. Th...

Nd0.5Bi2.5Fe4GaO12 (Bi2.5:NIGG) thin films with thicknesses of d = 200-1200 nm are prepared on Nd2BiFe4GaO12 (Bi1:NIGG) buffer layers on glass substrates using metal-organic decomposition. The shapes of the Faraday rotation spectra and hysteresis did not change with an increasing film thickness. The Faraday rotation angles increased in proportion w...

Nd2BiFe5−xGaxO12 thin films with the Ga composition x = 0, 0.5, and 1.0 are prepared on (001) oriented gadolinium gallium garnet substrates by a metal organic decomposition method. Only (001) peaks are observed in x-ray diffraction patterns for all the films, suggesting that the highly oriented Nd2BiFe5−xGaxO12 thin films were formed. Increasing Ga...

We present a new type of aperture antenna with V-groove structures that are made of Au to enhance strong circularly polarized light (CPL). Simulations using the finite element method revealed that strong CPL was enhanced within the aperture with a diameter of 10 nm. The intensity of the electric field was enhanced and was 22,700 times greater than...

We have successfully fabricated a basic magneto -optical spatial light modulator (MO-SLM) device driven by spin-transfer-switching (STS), which we call Spin-SLM technology. The SLM device is comprised of a one dimensional ten-pixel light modulation array (1 $\times$ 10 pixels) with a fine pitch of 1 $\mu{{m}}$ . The light modulation pixels were com...

A new semiconductor material, which comprises a solid solution of a ternary diamond-like semiconductor and transitional element Mn, was grown and studied. According to X-ray diffraction data, the crystal structure of the material is similar to that of the CdGeP2 host substance with a chalcopyrite-type crystal structure. The interplanar distances an...

Magneto-optical (MO) imaging plates consisting of bismuth-substituted rare-earth iron garnet (Bi:RIG) films were studied. Bi:RIG films were prepared both on gadolinium gallium garnet (GGG) single-crystal and glass substrates by metal-organic decomposition. MO properties, Faraday rotation hysteresis, and Faraday spectra were measured. The MO imaging...

We measured the distribution of surface plasmon polaritons (SPPs) on cross grooves fabricated in Au film by apertureless scanning near-field optical microscopy (aSNOM). SNOM signals around horizontal and vertical grooves had double peaks and a single peak, respectively. To understand these different behaviors, we carried out simulations by the fini...

Co ferrite thin films were prepared on MgO (100) substrates by metal organic decomposition (MOD). Crystalline structure, surface morphology, magnetic properties, and composition were investigated. The X-ray diffraction (XRD) pattern of the Co ferrite thin films indicates that CoFe2O4 was grown. A transmission electron microscopy measurement reveals...

The fluctuation conductivity above Tc (the paraconductiviy) in films of Bi2Sr2CaCu2O8+d (Bi2212) and YBa2Cu3O7-≏ (YBCO) with Tc variations is analyzed in terms of theoretical formulae based on the d-wave superconductivity. It is found that experimental data are describable by the Aslamazov-Larkin term provided that a total-energy cutoff effect is t...

Present status and Problem of MO-SNOM (Seminar Text for Applied Magnetics) in Japanese History of development of scanning near-field magneto-optical microscope (MO-SNOM) is briefly reviewed and application of the MO-SNOM to observation of recorded marks on MO disk is described in detail.(In Japanese)

A first-order beam diffracted by periodic arrays of GMR structures consisting of Pt/Co free layers having perpendicular magnetization without a top electrode is investigated. Linear and two-dimensional arrays of various shapes having sizes of 10–50 μm and periods of 20–100 μm embedded in SiO2 are fabricated. The angles of the plane of polarization...

We studied Nd3-XBiXFe4GaO12 films to obtain perpendicular magnetic anisotropy as well as large Faraday effect. NdBi2Fe4GaO12 (Bi2:NIGG) and Nd0.5Bi2.5Fe4GaO12 (Bi2.5:NIGG) films were obtained on Nd2BiFe4GaO12 (Bi1:NIGG) layer prepared on glass substrates by metal-organic decomposition (MOD) method. Bi2:NIGG and Bi2.5:NIGG films showed large Faraday...

Polarization properties in aperture-less scanning near-field optical microscopy (SNOM) were investigated using the 3D finite-difference time-domain (FDTD) method. We found that scattered light became elliptically polarized with linear or circular-polarized light illumination, and the polarization state of scattered light was preserved. In addition,...

We report on the preparation and characterization of Bi2Sr2CaCu2O8+d (Bi2212) thin films. These films on SrTiO3 substrates were fabricated by the metal-organic decomposition method and annealing at a temperature between 810~850 °C. On the basis of the analysis for the fluctuation conductivity σ’ above Tc, we characterize properties of Bi2212 films...

This paper presents future display systems, such as, bendable flexible display with plasma technologies and a spatial light modulator driven by spin polarized current (Spin-SLM) for 3D holography TV. As a flexible display, a Luminous Array Film (LAFi) with the plasma tube is the world first film type display that realizes a bendable super large are...

We studied the polarization state in an apertureless scanning near-field microscopy (a-SNOM) operating in reflection mode by using three-dimensional Finite-difference Time-domain (FDTD) method. As a result, the electric field around tip apex in the near-field region enhanced four times stronger than the incident light for p-polarization when the ti...

The switching field distributions in GMR devices with GdFe free layers of Si/Ru (3 nm)/Cu (75 nm)/Ru (3 nm)/Cu (70 nm)/Ru (13 nm)/TbFeCo (10 nm)/CoFe (1 nm)/Ag (6 nm)/ GdFe (16.5 nm)/Ru (3 nm) were studied by using high-resolution magneto-optical (MO) microscopy. The MO images of patterns with shapes of circles, triangles, squares and hexagonals, a...

Y0.5Bi2.5Fe5O12 (Bi2.5:YIG) films were prepared on glass substrates by metal-organic decomposition method. Bi2.5:YIG films were grown on buffer layers of Y2BiFe5O12, Gd2BiFe5O12, or Nd2BiFe4GaO12 (Nd-buffer layer) prepared on the glass substrates, while it was not obtained without buffer layers. It was found that Bi2.5:YIG films on Nd-buffer layer...

Magneto-optical properties of Si sub./(Ta/Cu)2/(Pt/Co) multilayer/X/indium zinc oxide (IZO) (X = Ta, Au, Pt, Ru, and Ag) are studied. Kerr rotations, reflectivities and figures of merit of the structures are compared with those of (Ta/Cu)2/(Pt/Co) multilayer/X (X = Ta, Au, Pt, Ru, and Ag) with IZO layers calculated by the virtual optical constant m...

We have developed a magneto-optical spatial light modulator (MOSLM) using giant magneto-resistance (GMR) structures for realizing a holographic three-dimensional (3D) display. For practical applications, reconstructed image of hologram consisting of GMR structures should be investigated in order to study the feasibility of the MOSLM. In this study,...

We developed a reflection-mode scanning near-field optical microscopy (SNOM) with an apertureless probe with a high special resolution and a high extinction ratio. Patterned Chromium film with a checker pattern deposited on a quartz substrate was measured. In SNOM images, clear contrast between Chromium and quartz was obtained, and the spatial reso...

抄録 Polycrystalline Bi3Fe5O12/BiY2Fe5O12 magneto-optical thin films were prepared by using a metal-organic decomposition (MOD) method on glass substrates. This was achieved by using YIG buffer layers, that is, BiY2Fe5O12 films, which allow bismuth and iron oxides to take a garnet structure. The samples were characterized by X-ray Diffraction (XRD) a...

We have investigated the spin transfer switching (STS) properties of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with various compositions of Gd-Fe free-layers for magneto-optical light modulator applications, whereby iron (Fe) concentrations are varied from 72.5 to 80.3 at. %. Switching current densities decreased dram...

Ternary diamond-like compounds in II–IV–V2 semiconductor system heavily-doped with transition d-element Mn have been recently prepared. The materials grown in both forms — single crystal layers and polycrystalline bulks — exhibit well defined ferromagnetic hysteresis with a saturation behavior in the magnetization curve up to above room temperature...

A study of the paraconductivity is adopted to characterize material properties in evaporated YBa2Cu3O7−δ films and melt-textured RBa2Cu3O7−δ superconductors with R=Y, Gd or Sm element, having different values of Tc and critical current density or trapped magnetic field. The paraconductivity is analyzed in terms of theoretical expressions for Aslama...

The crystallization process of bismuth substituted yttrium iron garnet (BixY3−xFe5O12; x = 0, 1, 2) powder prepared by the metal-organic decomposition method has been studied with various sintering temperatures. The pure garnet phase was observed for the x = 1 powder at 900 °C sintering temperature, whereas the x = 0, 2 powder showed secondary phas...

A magnetic field shifter for the evaluation of garnet film which is used as a readout head for magnetic media has been developed. The shifter enables to generate a sinusoidal magnetic field along one direction with a magnitude of up to 60 Oe and to move the magnetic field at any speed from few cm/s to 80 m/s. The garnet film to be evaluated was pla...

The crystallization of bismuth substituted yttrium iron garnet (Bi-YIG) powder and thin film prepared by the metal-organic decomposition method (MOD) have been studied. In the powder analysis, it was observed that the pyrolysis of metal-organic compounds begins at 250 °C and completed at 450 °C from the thermo-gravimetric-differential thermal analy...

Co/Pt multilayered films with perpendicular magnetic anisotropy have a large magneto-optical Kerr effect. To use the films with a submicron magneto-optical light modulator driven by spin transfer switching, we fabricated two types of magnetic tunnel junctions (MTJs) with Co/Pt multilayered films for the free layers. One is an fcc-based MTJ, another...

As a light modulating device used in high resolution magneto-optical spatial light modulator (MO-SLM), giant magneto resistance (GMR) devises driven by spin-injection is promising. In this paper, we report on optical and magneto-optical (MO) properties of GMR films, Si/SiO2/bottom electrode/TbFeCo (9 nm)/Cu (4 nm)/(Pt/Co (6 nm))/X (X = Ta, Au, Pt (...

Bi2.5Y0.5Fe5O12 and Bi3Fe5O12 thin films were prepared on Gd3Ga5O12 substrates using a metal organic decomposition (MOD) method as magneto-optical indicators (MOI) to visualize the distribution of magnetic flux. Their structural and magneto-optical properties were studied. The Faraday rotations of Bi2.5Y0.5Fe5O12 and Bi3Fe5O12 thin films were 15.5...