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Here we report on designing a magnetic field sensor based on magnetoplasmonic crystal made of noble and ferromagnetic metals deposited on one-dimensional subwavelength grating. The experimental data demonstrate resonant transverse magneto-optical Kerr effect (TMOKE) at a narrow spectral region of 50 nm corresponding to the surface plasmon-polaritons excitation and maximum modulation of the reflected light intensity of 4.5% in a modulating magnetic field with the magnitude of 16 Oe. Dependences of TMOKE on external alternating current (AC) and direct current (DC) magnetic field demonstrate that it is a possibility to use the magnetoplasmonic crystal as a high-sensitive sensing probe. The achieved sensitivity to DC magnetic field is up to 10−6 Oe at local area of 1 mm2.

We developed a three-dimensional (3D) holographic display using the magneto-optical effect. The system uses a microlens array to reduce the area size of light reflected from pixels of a digital mirror device to approximately 1 μm and write in parallel to a magnetic recording medium as hologram data. This method makes it possible to write over a wide area even with a piezo stage that has high resolution but a narrow range of movement. The holograms, written at a pixel pitch of 1.1 um, enabled the reconstruction of 3D images with a wide viewing angle of 26.7 deg. By avoiding abrupt directional changes of the piezo stage, the image quality was improved by eliminating line defects in the written holograms; image distortion was reduced by setting the incident angle of the reference light in the program of a computer-generated hologram to match the model and the reconstructing optical system. Image distortion was reduced by improving the program of the computer-generated hologram.

We demonstrate a logic gate based on interference of forward volume spin waves (FVSWs) propagating in a 54 nm thick, 100 μm wide yttrium iron garnet waveguide grown epitaxially on a garnet substrate. Two FVSWs injected by coplanar waveguides were made to interfere constructively and destructively by varying their phase difference, showing an XNOR logic function. The reflected and resonant waves generated at the edges of the waveguide were suppressed using spin wave absorbers. The observed isolation ratio was 19 dB for a magnetic field of ~2.80 kOe ( = 223 kA m−1) applied perpendicular to the film. The wavelength and device length were ~8.9 μm and ~53 μm, respectively. Further, the interference state of the SWs was analyzed using three-dimensional radio frequency simulations.

Magnetoelectric multiferroic nanocomposites are increasingly attracting attention from researchers and engineers due to their transformative technological potential. Many papers have so far reported a fundamental understanding and designs of new multiferroic nanocomposites, and their potential applications. However, many challenges for establishing and expanding their applications remain, for example, the development of an affordable fabrication process for nanocomposites which show room temperature multiferroics with robust coupling between ferroelectricity and magnetism is one of the highest demands. In this work, an affordable liquid phase based method to fabricate a magnetoelectric multiferroic nanocomposite film is reported. Ferroelectric BaTiO3 (BTO) nanotube arrays are fabricated via anodization and hydrothermal treatment, and then spin-coated with ferrimagnetic CoFe2O4 (CFO) to obtain a BTO–CFO nanocomposite film. The film exhibits not only room-temperature multiferroicity but also perpendicular magnetic anisotropy.

A nonlinear spin-wave (magnonic) logic gate based on the ferrite-film Mach-Zehnder interferometer was realized. The gate has two inputs and one output. The principle of operation of the device is based on the power-dependent phase shift of spin waves propagating in an yttrium iron garnet film. A XOR logic functionality for two digital data streams supplied to the gate inputs is shown. No control signal is needed for the gate operation. The performance characteristics of the device are discussed. Reliable functionality in the pulsed regime at 50 and 250 kb/s is demonstrated.

Strong- and broadband-spin wave (SW) excitation/detection structures are useful for magnonic devices. In particular, such structures are essential for observing magnonic bandgaps of magnonic crystals (MCs). Therefore, this study proposes a manufacturable broadband-SW excitation/detection antenna structure suitable for evaluating MCs. The antenna structure comprises a microstrip line fabricated on a yttrium iron garnet on a metal-covered silicon substrate. Calculations were performed using a three-dimensional finite integration technique and dispersion curves of SWs. The proposed structure exhibited high performance because of the significantly short distance between the signal line and ground plane. The generated bandwidth was ∼1.69 GHz for the 8.9 μm-wavelength SW at a frequency of 4 GHz. This work proposed an appropriate antenna structure for observing magnonic bandgaps, showing high potential for the development of MCs in integrated SW devices.

An induced nonlinear phase shift of spin waves excited in an yttrium iron garnet film waveguide has been studied. Experiments were performed with two microwave magnonic signals, being operating and pumping waves, co-propagated at different frequencies. The results show that a nonlinear phase shift up to 180° for the low-power operating wave is induced when increasing the pump-wave power. A theory describing the induced nonlinear phase shift is developed taking into account four-wave parametric coupling and nonlinear damping of two waves. The observed phenomenon paves the way to elaborate different types of nonlinear magnonic logic circuits.

Owing to their unique characteristics, multiferroic materials are expected to be widely used in the next-generation multifunctional devices. In addition to improving their characteristics, developing affordable fabrication processes for multiferroic materials is highly demanded in both industry and academia. In this paper, we show a novel process named electric-assisted magnetophoretic deposition for the fabrication of nanotube array-based multiferroic nanocomposite films. Magnetic nanoparticles were homogeneously deposited on the inner walls of the nanotube array substrate. A BaTiO3-CoFe2O4 nanotube array-based multiferroic nanocomposite film prepared in this work exhibited a magnetoelectric effect originating from the strain transfer between the two components.

Structural Magnetostrictive Alloys: From Flexible Sensors to Energy Harvesters and Magnetically Controlled Auxetics

In the fifty years since the postulation of Moore’s Law, the increasing energy consumption in silicon electronics has motivated research into emerging devices. An attractive research direction is processing information via the phase of spin waves within magnonic-logic circuits, which function without charge transport and the accompanying heat generation. The functional completeness of magnonic logic circuits based on the majority function was recently proved. However, the performance of such logic circuits was rather poor due to the difficulty of controlling spin waves in the input junction of the waveguides. Here, we show how Snell’s law describes the propagation of spin waves in the junction of a Ψ-shaped magnonic majority gate composed of yttrium iron garnet with a partially metallized surface. Based on the analysis, we propose a magnonic counterpart of a core-cladding waveguide to control the wave propagation in the junction. This study has therefore experimentally demonstrated a fundamental building block of a magnonic logic circuit.

Hologram memory is a strong candidate for optical storage due to its high recording density and high data transfer rate. We have studied and engineered a magnetic hologram memory medium using a stable magnetic garnet as recording material. To record a deep and clear magnetic hologram, it is important to control the heat diffusion generated during recording. Numerical simulation suggested that a multilayer structure with transparent heat-dissipation layers would be effective to address this. We fabricated a multilayer magnetic medium for a collinear magnetic hologram. This medium exhibited a diffraction efficiency as high as that of the single layered one, and errorless recording and reconstruction was achieved with the magnetic assist technique.

A one-dimensional magnonic crystal for forward volume spin waves (FV SWs) is demonstrated using eight pairs of Cu stripes fabricated on a 1-mm wide × 14-mm long × 10.2-µm thick yttrium iron garnet (YIG) waveguide and a SW absorber of 30-nm-thick Au film. The development of this crystal is challenging due to strong spectral oscillations caused by edge reflections and process difficulties associated with YIG magnonic crystals. A magnonic band gap with a depth of −4.6 dB is observed at a frequency of 1.80 GHz for a FV SW excited by a 50-µm-wide microstrip line, which is in good agreement with simulation results using three-dimensional modeling in the radio frequency region. The obtained performance is illustrated by plotting the depth of the respective band gaps vs the pair number of the stripes. This value is compared with that obtained in previous studies.

Magnetoplasmonic crystals consisted of a combination of noble and ferromagnetic thin films deposited on the diffraction gratings represent a special class of nanostructures that can utilize the magneto-optical Kerr effect enhanced by surface plasmon-polaritons excitation for the probing of an external DC magnetic field. Optical and magneto-optical properties of a magnetoplasmonic crystal are formed by magnetic behavior. This article represents the ways to manipulate the optical, magneto-optical and magnetic properties of nickel-based magnetoplasmonic crystals by the variation of the substrate parameters, the composition of magnetoplasmonic crystals as well as the compressive mechanical stresses on the surface of a ferromagnetic layer.

Magneto-optical (MO) effects enable non-reciprocal optical components like optical circulators and isolators as well as a magneto-optical spatial light modulator with switching speeds superior to a digital micromirror and a liquid crystal device. To develop a magneto-optical device with high performance, it is desirable to use materials with large rotation angles and small extinction coefficients. In other approaches introduction of nanostructures, magnetophotonic crystals [1] and localized surface plasmon resonance (LSPR) [2] has been shown to provide enhancement of the Faraday effect for distinct wavelengths. This work shows how rectangular arrays of gold (Au) particles embedded into thin films of bismuth-substituted yttrium iron garnet (Bi:YIG) offer different phenomena in comparison with the square arrays previously studied [3] [4] [5]. This enhancement of Faraday rotation was first observed in samples fabricated and characterized experimentally [6].

In connection with the developments of information technology (IT), thick electronic ceramic films have become important constitutive materials for various IT devices and systems. For instance, good piezoelectric or ferromagnetic thick films having thickness from several microns to several hundreds microns are required in MEMS microactuator devices, optical devices, and high-frequency devices. It is well known that good electronic ceramic films whose thickness is approximately less than 1 μm can be formed by means of physical or chemical methods including sputtering and CVD. On the other hand, ceramic bulks with good electrical or magnetic properties are obtained by sintering.

Planar magnetoplasmonic nanogratings composed of a two-dimensional square array of gold nanoparticles embedded into thin magnetic garnet films are proposed for enhancement of the transverse magneto-optical Kerr effect due to excitation of a quasi-waveguiding mode with light concentrated mostly inside the magnetic film. A proper optimisation of the size and periodicity of plasmonic nanoparticles as well as the thickness of magnetic dielectrics allows spectral tuning of the waveguiding mode leading to the sharp asymmetric resonance in the magneto-optical response in the desired spectral region.

Diode-pumped solid-state micro lasers are compact (centimetre-scale), highly stable, and efficient. Previously, we reported Q-switched lasers incorporating rare-earth substituted iron garnet (RIG) film. Here, the first demonstration of the magnetooptical (MO) Q-switch in an Nd:YAG laser cavity is performed. We fabricate a quasi-continuous-wave (QCW) diode-pumped Nd:YAG laser cavity, which is shortened to 10 mm in length and which contains an RIG film and a pair of small coils. This cavity yields a 1,064.58-nm-wavelength pulse with 25-ns duration and 1.1-kW peak power at a 1-kHz repetition ratio. Further, the polarisation state is random, due to the isotropic crystal structure of Nd:YAG and the fact that the MO Q-switch incorporating the RIG film does not require the presence of polarisers in the cavity. This is also the first report of an MO Q-switch producing random polarisation.

Thin film oxide materials often require thermal treatment at high temperature during their preparation, which can limit them from being integrated in a range of microelectronic or optical devices and applications. For instance, it has been a challenge to retain the optical properties of Bragg mirrors in optical systems at temperatures above 700 °C because of changes in the crystalline structure of the high–refractive-index component. In this study, a ~100 nm–thick amorphous film of tantalum oxide and yttrium oxide with an yttrium-to-tantalum atomic fraction of 14% was prepared by magnetron sputtering. The film demonstrated high resistance to annealing above 850 °C without degradation of its optical properties. The electronic and crystalline structures, stoichiometry, optical properties, and integration with magnetooptical materials are discussed. The film was incorporated into Bragg mirrors used with iron garnet microcavities, and it contributed to an order-of-magnitude enhancement of the magnetooptical figure of merit at near-infrared wavelengths.

Magnetic holographic memory is expected as a rewritable high-capacity data storage technology. To improve the reconstructed image, we investigate recording conditions by numerical simulation and experiments. We found experimentally that four diffracted beams from a digital micromirror device interfere with each other at a suitable defocus recording point, and such overlapping is favorable to obtain clear reconstruction images without diffuser. Subsequently, we modify the shape of the reference beam to ensure more effective interference. As a result, we achieve error-free image reconstruction from the magnetic hologram. Our results indicate that magnetic holograms can potentially be utilized as holographic memory.

We have observed the Fano-type Faraday rotation spectrum in a one-dimensional magnetophotonic crystal at the Bloch surface wave (BSW) resonance and found that it is a result of the coupling between the $s$-polarized BSW and the $p$-polarized waveguiding modes of the magnetophotonic crystal. The shape of the resonance is determined by the relative position and spectral splitting of the modes.

Hologram memory is expected to be the next-generation of optical data storage technology. Bismuth-substituted yttrium iron garnet is typically used for rewritable magnetic hologram media. The diffraction efficiency of magnetic holography depends on the Faraday rotation angle, but the experimental diffraction efficiency is not as high as that expected from calculations. This difference could be caused by incomplete magnetization reversal at the recorded region. In this study, we investigated the effects of magnetic assist (MA) recording through numerical simulation and experiment to improve the diffraction efficiency and the resulting reconstructed images. The improvement of diffraction efficiency was more effective in garnet films thinner than the width of a fringe, and a suitable value of the assist magnetic field was identified for the improvement. In addition, MA recording improved the intensity of reconstructed images and broadened the non-error recording conditions to the low energy region. This technique shows promise in improving the reconstructed quality of magnetic hologram data.

Slow light is a phenomenon explained by low group velocity of the pulsed light. Faraday effect can be greatly enhanced in multilayered structures due to the artificial dispersion [1, 2]. Magnetophotonic crystals, as being layered nanostructures, can modulate electric filed amplitude and phase of a femtosecond pulse in time. For example, Faraday angle at the initial part of the pulse can differ from that at its tail, and from the steady-state value. In this work femtosecond dynamics of Faraday rotation is demonstrated experimentally in magnetophotonic crystals by polarization-sensitive correlation spectroscopy.

Both polycrystalline and single-crystal films of iron-substituted strontium titanate, Sr(Ti0.65Fe0.35)O3-delta, prepared by pulsed laser deposition, show room-temperature magnetism and Faraday rotation, with the polycrystalline films exhibiting higher saturation magnetization and Faraday rotation. The magnetic properties vary with the oxygen pressure at which the films are grown, showing a maximum at pressures of approximately 4 mu Torr at which the unit-cell volume is largest. The results are discussed in terms of the oxygen stoichiometry and corresponding Fe valence states, the structure and strain state, and the presence of small-volume fractions of metallic Fe in single-crystal films grown at the optimum deposition pressure. Integration of magneto-optical polycrystalline films on an optical-waveguide device demonstrates a nonreciprocal phase shift., JST PRESTO, JSPS Postdoctoral Fellowships for Research Abroad; NSF; FAME; DARPA; MARCO; Center for Development of Nanoscience and Nanotechnology, CEDENNA, Chile; Fondecyt; DGIIP USM, Chile; JSPS; Center for Materials Science and Engineering (CMSE)

~0.8 μm thick rare-earth substituted iron garnet films were grown on single crystalline Nd:YAG substrates using pulsed laser deposition for integration of active magnetooptical Q-switches with microchip lasers.

A 1-μm thick Ce substituted yttrium iron garnet film was grown on (111) Nd:YAG substrate directly via pulsed laser deposition method for integrated magnetooptical Q-switch lasers. Magnetization properties, structural analysis using x-ray diffractions, and magnetooptical properties were characterized. The film was oriented (111) direction, and the easy axis of magnetization was oriented for in-plane of the film. The film showed a large Faraday rotation angle of −0.05 deg/μm at the wavelength of 1064 nm.

We have developed magneto-optic spatial light modulators (MOSLMs) with submicrometer-size magnetic pixels for wide-viewing-angle holographic displays (3-D-MOSLM) that are driven by the thermomagnetic recording. The holographic images were reconstructed by the magnetic hologram pattern on the MOSLM. In this paper, we have studied colorization of reconstruction images of the MOSLMs using optical space division method. This method used some 3-D-MOSLMs to represent intermediate colors. The magnetic films were polycrystalline bismuth, dysprosium, and aluminum substituted yttrium iron garnet (BiDyYFeAlG) films with perpendicular magnetization. The thickness of BiDyYFeAlG films was designed for each wavelength. The MOSLM represented (3-D) images with intermediate colors that were synthesized 3-D images with red and green colors. In addition, tones of intermediate colors were represented by controlling intensity of each reference light. These results demonstrated that 3-D-MOSLMs have promise for full-colorized holographic 3-D displays.