نشریه اپتوالکترونیک
سال چهارم شماره 2 (پیاپی 11، بهار و تابستان 1401)

In this study, the structural, electronic and magnetic properties of new full Heusler alloys Ir2VZ (Z = Si, Ge, Sn) were studied using the Quantum Espresso software package based on density functional theory. Interchanging the positions of atoms, the calculations were performed for two hypothetical L21 and XA structures. The results showed that, the XA structure of alloys was non-magnetic, while the L21 structure of these alloys was ferrimagnetic. Based on investigation of structural properties of these alloys, it was found that the Ir2VSi alloy is more stable than the other two alloys due to its lowest cohesive energy. Also, the results of calculations on electronic properties show that Ir2VSi, Ir2VGe and Ir2VSn alloys are half-metall, quasi half-metall and metall at equilibrium lattice constants, respectively. Thus Ir2VSi alloy has 100% spin polarization around the Fermi level and its total magnetic moment (3µB/f.u.) exactly follows Slater-Pauling rule.

In this work, for the first time, the qualitative behaviors of squeezing and entanglement in quantum two-mode squeezed radars (QTMS) when the target is present and the signal is transmitted to the target are calculated and their qualitative behaviors are evaluated. The squeezing parameter is a tool in theory similar to the laboratory's signal power. Therefore, the correlation between signal-idler increases or decreases with signal power changes. This increase or decrease of correlation (especially entanglement) leads to improvement or weakening of the performance of quantum radars. In this work, it can be seen that with the increase of the squeezing parameter even at room temperature (300 K), the behavioral quality of the squeezing increases, and hence, the correlation between the signal and the idler also increases. We also examine the entanglement, where we see that there is a maximum limit to increase in signal power that cannot be exceeded, however, this limit can be violated by choosing a suitable receiver, hence at high powers maintained entanglement. Therefore, by controlling the squeezing parameter and choosing a suitable receiver, which leads to the improvement of squeezing and entanglement behaviors, the performance of a QTMS radar can be optimized at room temperature.

Fe3O4 nanoparticles were fabricated by co-precipitation method with stoichiometric and non-stoichiometric ratios in air atmosphere and temperature of 78 °C. Structural analysis of the samples was performed by X-ray diffraction pattern (XRD). The magnetic properties of the nanoparticles were investigated using an alternating force gradient magnetometer (AGFM) and Faraday scale. The XRD patterns indicated that the specimens were single phase and the cubic phase of the magnetic spinel was formed. The diffraction peaks of the XRD pattern are consistent with the reference card 0866-088-01 for the magnetite phase. For non-stoichiometric ratios,  by increasing Fe2+/Fe3+, the Cure temperature decreases compare to the bulk sample (585 °C), due to the decrease in particle size. As the particle size decreases, the number of super-exchange interactions between the sites of the spinel crystal structure decreases. Therefore, by increasing the ratio of divalent iron cation to its trivalent cation, nanoparticles with saturated magnetism and similar coercive force and different Curie temperature can be produced and with less heat energy, the order of the spins is disturbed and the transition from the ferromagnetic phase to the paramagnetic phase occurs. The Raman spectra for the  samples showed specific peaks related to the magnetite structure at 336 cm-1 and 490 cm-1 wave number. Comparison of the Raman spectroscopy of the samples after applying the magnetic field indicated an increase in the number and height of the peaks, which was due to the orientation of the nanoparticles in the direction of the magnetic field.

Impact of minor substitution of carbon on microstructure, magnetic properties and hyperfine interactions of Fe–Si–B–Cu-type metallic glasses was investigated. For this purpose, samples of Fe83.3Si4B12Cu0.7 and Fe83.3Si4B11Cu0.7C1 compositions were prepared using melt spinning technique. Then, to study different characteristics of samples, X-ray diffraction, differential scanning calorimetry, magnetic thermogravimetry, scanning electron microscopy, Mӧssbauer spectrometry, and magnetic measurements were applied. Fully amorphicity of the samples and a larger heat treatment temperature range of the C-containing sample was found. Though minor carbon introduction had negligible effect upon average values of hyperfine magnetic fields and chemical short-range order, structural deviation in topological short-range order was unveiled. No change was observed in saturation magnetization, however, the amount of coercive field in the case of perpendicular external magnetic field decreased significantly.

Using the density functional theory, the electronic, magnetic and optical properties of Ti2ScGe have been investigated. The first thing that should be examined is the stable structure for the full-Heusler compound, after the investigations, a structure named type a was considered in the ferromagnetic state. This compound is studied for the first time in this paper and in the investigated conditions, it was recognized as a ferromagnetic half-metallic with a half-metallic gap of 0.4 electron volts. This compound has several acceptable factors for its applicability in making spintronics devices. Such as, half-metallic properties, high Curie temperature around 1086 K, its stability in the ferromagnetic state, and following the Slater-Pauling rule. Also, the examination of the optical properties showed that the Ti2ScGe full-Heusler compound can be further studied as a wave absorber

potential candidate for using in spintronic and optoelectronic devices. Using first principle calculations based on density functional theory within generalized gradient approximation (GGA), we studied the elastic,mechanical, electronic, magnetic and optical properties of NbBiCs half-Heusler alloy in bulk state. Spin polarization at Fermi level is 97.6% and 100% whitin GGA and GGA+mBJ, respectively. The real part of the dielectric function for half-Heusler alloy NbBiCs in α phase for energies greater than 20eV converge to one, indicating that it act as an isotropic insulator and also the refractive index for energies greater than 7.5 eV is less than one, indicating super-liminance.

The induction of magnetization in two-dimensional dichalcogenide materials is one of the potentials of these materials in the manufacture of spintronic devices. Using basic principles calculations and using the 3d transition metal doping technique, the magnetic property of the single-layer dichalcogenide 1T-NiTe2 was investigated. Results It shows that doping transition metals V, Cr, Mn, and Fe magnetize the structure. The highest and lowest values of induced magnetization are related to the Cr atom and Fe atom, respectively. Cr atoms form a ferromagnetic (FM) coating with adjacent nickel atoms and an antiferromagnetic (AFM) hybrid with telluride atoms. While the Fe atom has hybrid antiferromagnetism with nearby nickel and telluride atoms, which motivates less magnetization in the system.

In this paper, we have been used energy spectrum of ideal single layer graphene to investigate thermodynamic properties of this material. We have used Shannon and Tsallis entropies for investigating the entropy, internal energy and specific heat of this system. We plot these properties versus temperature. The obtained results show that the entropy and internal energy increase with enhancing the temperature and then these reach to a constant values. Also, the specific heat increases until it reaches a maximum and then reduces with increasing the temperature.

When metal nanoparticles are exposed to electromagnetic waves, they generate heat due to the interaction of surface conduction electrons of nanoparticles and their fluctuations, as well as the Joule heating effect. The emerging science of investigating heat produced by nanoparticles is called thermoplasmonics. The heat generated is remotely controlled by light. This generated heat increases the temperature in nanoparticles and the environment. Thermoplasmonics has many applications in various fields such as physics, chemistry, and medicine, and measuring the produced heat is complicated. This article studies the practical method of increasing the local electric field and producing heat by nanoparticles. Placing asymmetric hexagonal nanoparticles as an antenna or amplifier around a rectangular nanoparticle increases the light interaction with the middle nanoparticle. It causes an increase in the local electric field and generated heat by the middle nanoparticle.

In this article, we investigate photonic squeezed states with a special initial state. For this purpose, first, we consider a special initial state of two modes, then we squeezed one or two modes. In the following, we describe a method based on the Wigner function for the entanglement of the system, first we write the state of the system in the phase space using the Wigner function, and then apply the squeezing operator to the Wigner function of a system, next the state of the system transferred from the phase space to the Hilbert space. I do. In the end, we obtain the degree of entanglement for N=1,2 states by using concurrence. In this article, you can see the effect of the initial state and the number of modes used on the degree of entanglement of the system.

In this paper, the AND all-optical logic gates using of two-dimensional photonic crystals have been designed and simulated. In the proposed all-optical AND gate, photonic crystals are placed in a square lattice with dielectric rods in the air substrate, which are designed with "H" semi-shaped defects in order to achieve the requirements of high-speed networks. Also, the performance of the all-optical AND logic gate was analyzed using the finite difference time domain method. The plane wave expansion method was used to obtain the gap band structure. The results show that the AND logical gate proposed to work at 1550 nm optical wavelength with high contrast ratio and minimum delay time used in optical devices and potential applications in optical sensors and optical integrated circuits.

investigate the effect of the size of metal nanoparticles of gold, silver and copper on the nonlinear optical properties of glass. In this way, spherical nanoparticles with a volume fraction less than 0.1 (in order to ignore the interaction between them) are distributed in the glass, and using the T-matrix method, their effective dielectric coefficient is determined as a function of size ( radius) of nanoparticles and their volume fraction are obtained at different wavelengths. At the end, the relevant diagrams are drawn