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Technology and applications of spatial light modulators
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
The employment of the magneto-optic effect for spatial modulation is shown in Figure 7.11 [165–167]. The device, which is based on the magneto-optic effect associated with the magnetic domain reversal in a ferromagnetic material [gadolinium–gallium–garnet (GGG)], is electrically driven using conducting X–Y mesh-lines which form the boundaries of the magneto-optical pixels. As a particular mesh-node is cross-activated (i.e., both the X-line and the Y-line for that node) the resulting current flowing around that pixel corner generates a magnetic field, which causes a magnetic domain reversal in that magneto-optical pixel.
3D Magnonic Structures as Interconnection Element in Magnonic Networks
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
A. A. Martyshkin, S. A. Nikitov, A. V. Sadovnikov
Low packing density is one of the most vulnerable points of criticism of magnonic devices combined in magnonic networks since the attenuation of the spin-wave signal is a serious obstacle to the assembly of a computational unit limited to spatial scales commensurate with the SW propagation length. The use of magnetic films with the lowest decay rate is one of the approaches to overcoming these limitations – in particular, the use of yttrium iron garnet (YIG) films makes it possible to achieve the propagation length of a spin-wave signal up to several millimeters without significant losses. A typical spin-wave guide structure contains a non-magnetic substrate on which a magnetic film is grown. Gallium-gadolinium garnet (GGG) is most commonly used as a substrate material. To form a waveguide, there are a large number of methods for growing a magnetic film: in particular, liquid-phase epitaxy, deposition, and laser ablation. YIG most meets the requirements of low attenuation of the spin-wave signal since it has a narrow absorption line of ferromagnetic resonance (typically 0.5 Oe at 10 GHz). The simplest waveguide structures are confined in lateral direction magnetic films of YIG. High-efficiency control of spin-wave propagation in ultra thin yttrium iron garnet by the spin-orbit torque was considered in [5]. With the help of such structures, it became possible to excite the spin torque with efficient signal transmission over extended regions. Investigation of inhomogeneous tapered waveguide structures showed that, under the width constraint, it is necessary to take into account the multimode propagation of spin waves due to energy redistribution between modes [6, 7]. It should be noted that in magnonics, not only the Gilbert damping [1] but also the damping associated with the spin-wave scattering is important. The fabrication of magnonic waveguides also affects the spin-wave group velocity, which influences the signal attenuation [1, 8, 9].
Simultaneous harvesting of radiative cooling and solar heating for transverse thermoelectric generation
Published in Science and Technology of Advanced Materials, 2021
Satoshi Ishii, Asuka Miura, Tadaaki Nagao, Ken-ichi Uchida
In the current investigation, we prepared a device which is able to simultaneously harvest radiative cooling and solar heating in the daytime to generate transverse thermoelectric voltage by the SSE. This can be achieved with a sunlight-transparent and thermally emissive substrate at the top and sunlight absorbing layer at the bottom while having the SSE structure in the middle. The design is somewhat similar to a daytime radiative cooling structure which has separated thermal radiation and sunlight reflecting layers. However, in the prepared device, a sunlight absorbing layer was utilized instead of a sunlight reflecting layer at the bottom. For the proof-of-concept demonstration, we used a hybrid device consisting of a paramagnetic gadolinium gallium garnet (GGG)/ferrimagnetic yttrium iron garnet (YIG)/paramagnetic platinum (Pt) trilayer and blackbody (BB) paint where the GGG/YIG/Pt trilayer is a prototypical structure for the SSE. Critically, the GGG side was facing upwards during the measurements where the GGG and Pt/BB layers were the thermal radiation and sunlight absorbing layers, respectively. The outdoor measurements were verified by indoor measurements, which imitated outdoor conditions, and by numerical heat transfer simulations. Our investigation advances the practical applications of SSE devices, which are planar and scalable, to be used in self-power off-grid sensors within the era of Internet of Things (IoT).
Influence of Coal Petrography on Microwave-assisted Carbothermic Reduction Roasting of Banded Hematite Jasper Ore
Published in Mineral Processing and Extractive Metallurgy Review, 2021
Subhnit K. Roy, Deepak Nayak, Nilima Dash, Swagat S. Rath
Petrographic analyses of both coals (C1 and C2) used in the microwave roasting of BHJ ore were carried out according to the standard procedures (Stach 1975). The representative coal samples were crushed to less than 1 mm size for preparing the polished sections. A mixture of hardener and epoxy resin in the ratio of 1:5 was used for embedding the coal samples onto a mount followed by grinding and polishing. The petrographic studies were done on an advanced polarized microscope (Leica DM4500P) equipped with Microscope Spectroscopy System (MSP- 200), counting system (Petroglite), photometry system and fluorescence attachment. Recommendations of Stach (Stach 1982) and International Committee for Coal Petrology (International Committee for Coal Petrology 1971; The New Vitrinite Classification (ICCP System 1998) were taken into account for data interpretation and estimation of the volume percentage of various macerals along with mineral matter. Vitrinite reflectance analysis was conducted according to British Standards BS 6127–3 using Gadolinium-Gallium-Garnet (1.719%), Yttrium-Aluminum-Garnet (0.902%) and Sapphire (0.58%) calibration standards. Apart from this, the automated image analysis technique (Lester, Watts and Cloke 2002) was used to understand the micro-textural analysis of different macerals and mineral matter present in the coal samples.
Damage induced in garnets by heavy ion irradiations: a study by optical spectroscopies
Published in Philosophical Magazine, 2018
Jean-Marc Costantini, Sandrine Miro, Gérald Lelong, Maxime Guillaumet, Marcel Toulemonde
Pure and doped ferrimagnetic yttrium iron garnet (Y3Fe5O12 or YIG) was considered since long as an important material for opto-electronic applications and magnetic recording (‘bubble garnets’) [1]. Epitaxial films of rare-earth substituted iron garnets on gadolinium gallium garnet (Gd3Ga5O12 or GGG) substrates are still developed for magnetic or magneto-optical devices and micro-wave applications [2]. Ion irradiation or implantation is currently applied to tailor materials properties. In particular, for YIG, swift heavy ion irradiations, above a given threshold electronic stopping power (Se = (–dE/dx)e), produce amorphous tracks [3,4] that can change the microstructure and the magnetic or magneto-optical properties by pinning Bloch walls, and increasing coercive field and Faraday rotation [5,6].