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We report a novel and inexpensive fabrication process of multiferroic nanocomposite via liquid phase using an anodic alumina template. The sol-gel spin-coating technique was used to coat the template with ferrimagnetic CoFe2O4. By dissolving the template with NaOH aqueous solution, a unique nanotube array structure of CoFe2O4 was obtained. The CoFe2O4 nanotube arrays were filled with, and sandwiched in, ferroelectric BaTiO3 layers by a sol-gel spin-coating method to obtain the composite. Its multiferroicity was confirmed by measuring the magnetic and dielectric hysteresis loops.

Abstract 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.

Abstract 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.

Stress induced modulation of the diffraction angle and efficiency of the light reflected from a stripe-domain magnetic garnet was demonstrated. The spacing of the magnetic domain was changed using the inverse magnetostriction effect. The sample structure was a piezo actuator/Al reflection layer/magnetic garnet substrate. A diffraction angle between the 0th and 1st ordered light was changed from 9.12 deg. to 10.20 deg. This result indicates that the domain spacing was changed from 3.3 μm to 3.0 μm. The change of the diffraction angle was irreversible for the voltage. However, reversible, linear and continuous change of the diffraction efficiency was observed. These results could be applicable for a voltage-driven optical solid state light deflector with low power consumption and high switching speed.

Three-dimensional magneto photonic crystals (3D-MPCs) are promising material for manipulating light in 3D space. In this study, we fabricated 3D-MPC that is filling the air-gap of opal photonic crystal with magnetic material by electroless plating. The electroless plating is an attractive film-forming method which provides magnetic material films on various substrates in aqueous solution at 24-90 °C. As magnetic material for filling the air-gap, maghemite (γ-Fe2O3) film was plated in opal photonic crystal. The plated maghemite film showed a Faraday rotation of 0.6 deg./μm at 440 nm and significantly lower absorption than magnetite. The plated opal showed photonic band gap and magneto-optic response. Faraday rotation of the plated opal was enhanced at the band edge. The photonic band gap and the Faraday rotation spectra were changed as a function of incident angle of light. Electroless plating of maghemite could be promising technique for fabricating 3D-MPCs.

Bi-layered zinc oxide (ZnO) and bismuth substituted yttrium iron garnet (Bi:YIG) was fabricated and magneto-optically investigated. Enhancement of Faraday rotation and magnetic circular dichroism (MCD) was observed. The wavelength of MCD enhancement was in good agreement with exciton wavelength of ZnO. This enhancement was only observed in the bi-layer, and implies that the exciton generated in ZnO interacted with Bi:YIG. Because the exciton wavelength of ZnO can be controlled by electro-optic effect, this result has the potential for realizing voltage control of magneto-optic effect.

Holographic memory is a strong candidate for next-generation optical storage, featuring high recording densities and data transfer rates, and magnetic hologram memory using a magnetic garnet, as the recording material is expected to be used as a rewritable and stable storage technology. However, the diffraction efficiency of magnetic holography depending on the Faraday rotation angle is insufficiently high for actual storage devices. To increase the diffraction efficiency, it is important to record deep magnetic fringes, whereas it is necessary to suppress the merging of fringes owing to heat diffusion near the medium surface. In this work, we investigated the recording process of magnetic holograms in detail with experiments and numerical simulations, and developed a multilayer media with transparent heat dissipation layers to record deep and clear magnetic holograms by controlling the heat diffusion generated during the thermomagnetic recording process. To suppress lateral heat diffusion near the medium surface, we designed and fabricated a multilayer magnetic medium in which the recording magnetic layers are discrete in a film, approximately 12-µm thick. This medium exhibited diffraction efficiency higher than that of the single-layer medium, and error-free recording and reconstruction were achieved using the magnetic assist technique.

Spin waves (SWs) have the potential to reduce the electric energy loss in signal processing networks. The SWs called magnetostatic forward volume waves (MSFVWs) are advantageous for networking due to their isotropic dispersion in the plane of a device. To control the MSFVW flow in a processing network based on yttrium iron garnet, we developed a SW absorber using artificial structures. The mechanical surface polishing method presented in this work can well control extrinsic damping without changing the SW dispersion of the host material. Furthermore, enhancement of the ferromagnetic resonance linewidth over 3 Oe was demonstrated.

Zinc oxide (ZnO) is a promising material for combining with magneto-optic (MO) materials because it can propagate stable exciton-polaritons, with velocities considerably lower than that of photons in a vacuum. This study investigated the influence of sputtered ZnO and Al:ZnO top layers on MO responses of a bismuth-substituted yttrium iron garnet (Bi:YIG) film. The ZnO top layer modulated the Faraday rotation and magnetic circular dichroism (MCD) of the Bi:YIG around the exciton resonance wavelength of ZnO at 369 nm. Furthermore, Al-substituted ZnO, which is a conductive ZnO, also changed the MO effects around the exciton resonance wavelength. These results imply that the exciton-polaritons in ZnO affect the MO interaction, because of their considerably low group velocity. The results suggest potential for controlling the MO response via excitons.

A holographic memory has been attracting attention as recording media with high recording density and high data transfer rate. We have studied the magnetic garnets as a rewritable and long life media for magnetic holography. However, since the signal intensity of reconstructed image was relatively low, the effects of recording conditions on the diffraction efficiency of magnetic hologram were investigated with experiments and the numerical simulation using COMSOL multiphysics. The diffraction efficiency tends to decrease as increasing the spatial frequency, and the use of short pulse laser with the pulse width of 50 ps was found to be effective to achieve high diffraction efficiency. This suggests that the formation of clear magnetic fringe similar to interference pattern can be obtained by the use of short pulse laser since undesirable heat diffusion during radiation does not occur. On the other hand, the diffraction efficiency increased as increasing the film thickness up to 3.1 µm but was saturated in the garnet film thicker than 3.1 µm in the case of spatial frequency of 1500 line pair/mm. The numerical simulation showed that the effective depth of magnetic fringe was limited about 1.8 lm irrespective of the garnet film thickness because the fringes were connected by thermal diffusion near the surface of the film, and the effective depth is limited due to this connection of the magnetic fringe. Avoiding this fringe connection, much higher diffraction efficiency will be achieved. [ABSTRACT FROM AUTHOR]

We demonstrate the localization of magnetostatic surface waves, i.e., spin waves, in a onedimensional magnonic microcavity substantialized with periodical conductivity modulation. The narrow localized state is observed inside band gaps and is responsible for a sharp transmission peak. The experimental results strongly agree with the theoretical prediction made with the shape magnetic anisotropy of the propagating medium composed of yttrium iron garnet taken into account. [ABSTRACT FROM AUTHOR]

Magnonic crystals (MCs) are key components for spin wave manipulation. MCs realized with periodically metallized surfaces have an advantage in ease of the fabrication, but the effect of the metal thickness has not been studied well. In this work, the metal thickness dependence on the transmission spectra of localized mode spin waves was investigated. The metal thickness over half of the skin depth was necessary to prevent strong attenuation of spin waves. [ABSTRACT FROM AUTHOR]

We demonstrated the spin wave isolator using bilayer ferromagnetic media comprising single crystalline and poly-crystalline yttrium iron garnet films, which can control the propagation frequency of magnetostatic waves by the direction of applied magnetic field. This isolator's property does not depend on their thickness then this can be downsized and integrated for nano-scale magnonic circuits. Calculated dispersion relationship shows good agreement with measured one. [ABSTRACT FROM AUTHOR]

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Bismuth-substituted yttrium iron garnet (Bi:YIG)-based two-dimensional (2D) magnetophotonic structures were fabricated on top of opal thin films. Autocloning approach was used to transpose 2D hexagonal symmetry of the opal (111) plane into sputtered Bi:YIG. Resultant 2D patterned Bi:YIG films had two realizations. As-sputtered films had a hemispherical profile of structural elements. These films were additionally etched to obtain films with a cone profile of scatterers. Optical and magneto-optical spectra of the films demonstrated resonances addressed to diffraction from the patterned Bi:YIG films. Structural parameters of these magneto-optical gratings were found to govern the magnitude of Kerr rotation [ABSTRACT FROM AUTHOR]

A holographic display is a realistic three-dimensional (3D) display because it produces an exact copy of the wave front of scattered light from 3D objects. It demands a wide viewing angle for 3D visualization. However, the viewing angle of holographic displays based on conventional spatial light modulators (SLMs) is less than 3°. The pixel pitch of conventional SLMs is in the range of 10-100 µm. Recently, we have fabricated a two-dimensional pixel array with sub-micrometer-scale pixels for a wide-viewing-angle holographic display. The pixels were driven by a thermomagnetic recording system using a metal mask that formed fringe patterns. However, the reconstructions of 3D images were fixed. In this paper, we describe the results of the reconstruction of any 3D images using a tilling optical addressing method. The tilling optical method reproduced any magnetic fringe pattern with 5 x 107 pixels for the reconstruction of 3D images. [ABSTRACT FROM AUTHOR]

A magnetic-field sensor with a high sensitivity of 38 pT/Hz was demonstrated. By utilizing a spinwave differential circuit (SWDC) using two yttrium iron garnet (YIG) films, the temperature sensitivity was suppressed, and the thermal stability of the phase of the spin waves was -0.0095° K-1, which is three orders of magnitude better than a simple YIG-based sensor, ~20° K-1. The SWDC architecture opens the way to design YIG-based magnonic devices. [ABSTRACT FROM AUTHOR]

Thermal elasticity and electrical resistivity with the magnetic phase transition were studied in FeRh alloy films prepared by ion-beam sputtering and subjected to post-annealing. Fe49.7Rh50.3 and Fe48.9Rh51.1 films deposited on conventional glass substrate and subjected to post-annealing at 600 °C for 90 mm, respectively. Both films show a considerably sharp transition In particular, Fe49.7 Rh50.3 film exhibits small thermal hysteresis of about 20°C width, which is only about 2 times over than that of bulk. Furthermore, a large abrupt thermal strain over 2 × 10-3 was observed with the magnetic transition. These results indicate that strictly controlled an equlatomic composition is an effective way to obtain the FeRh film with abrupt magnetic phase transition under low temperature and short time annealing. [ABSTRACT FROM AUTHOR]

An extremely flat transmission band for a forward volume spin wave (SW) propagating in an SW waveguide composed of yttrium iron garnet film and SW absorbers was obtained, using the finite integration technique. Three-dimensional analysis of the calculated results showed that the transmission ripples of the SWs propagating in the waveguide were caused by SW interference, especially that due to two standing waves originating from the waveguide edge–edge and the waveguide–antenna edge. To suppress these waves, SW absorbers composed of gold film were introduced and the resultant positions and shapes were investigated precisely. Hence, an extremely flat transmission band was obtained. The results of this study have potential application in the development of one- and two-dimensional magnonic crystals for integrated SW devices. [ABSTRACT FROM AUTHOR]