SPIN

In this paper, we study the thermal and dielectric properties of a carbon-like nanotube structure. The ferrielectric mixed spin (1,3/2) Blume–Capel Ising model has been investigated, using Monte Carlo simulations under the Metropolis algorithm. We illustrate the thermal and dielectric properties of different physical parameters. Besides, we examine the effects of the exchange coupling interactions, the external longitudinal electric and the crystal fields on the transition temperature. It is found that the polarization decreases toward a transition temperature and undergoing the paraelectric phase, faster for low values of the external longitudinal electric field and the exchange coupling interactions. Besides, the total polarization versus the crystal field undergoes two principal transitions and exhibits a first-order and a second-order transitions.

In this work, the Monte Carlo simulations have been performed to investigate the magnetic properties of the kesterite and the stannite nanostructures with mixed spins. The Blume–Capel model has been adopted to study the Cu₂ZnSnSe₄ nanostructures. Furthermore, we have examined different transitions as a function of the temperature, the crystal field, and the exchange coupling interactions. Also, the behavior of the magnetizations and magnetic susceptibilities are investigated as a function of the different physical parameters. A comparison of the magnetic properties of each nanostructure has been studied and discussed.

In this paper, we fabricated graphene/Fe₃O₄ heterostructure devices by stacking monolayer graphene on magnetite (Fe₃O₄) substrate and investigated their magneto-transport properties. Interestingly, graphene/Fe₃O₄ heterostructure devices exhibit a giant magnetoresistance (MR) of 70% at a low magnetic field of 0.65T and at 11K, which is three times greater than that of graphene on SiO₂. Based on standard two-fluid model and LDA$+$U simulation, we showed that the observed enhanced MR effect is due to the increased disorder in graphene induced through the charge polarization via the alignment of C atoms of graphene over the charge ordered B-site cations of Fe₃O₄. Our results demonstrate a potential way to enhance graphene MR effect through coupling graphene with a suitable substrate with charge orbital ordering.

Using the finite cluster approximation (FCA) based on a single-site cluster theory and Monte Carlo simulation (MCS) under the Metropolis algorithm, we study the critical properties of two-dimensional (2D) spins-½ system by analyzing the effect of the anisotropic parameter $a$ and next-nearest-neighbor (NNN) interaction $J^{\prime \prime }$ on the critical temperature $T_C$ of the 2D anisotropic square lattice. It is found that the MCS is more reliable than the FCA method in the resolution of the Ising model. Moreover, MC calculations reveal that $Tc$ is strongly correlated with the external magnetic field $h$, $a$, and $J^{\prime \prime }$, where the competition between these parameters can generate several rich phase diagrams.

The emerging need for new functional materials has recently been engaged in a large quest to predict the alternative green and low-cost energy industry. To this end, thermoelectric as well as spintronic applications remain challenging. In this study, we present, for the first time, a density functional calculation on the IrFeSi half-Heusler compound. The calculation gives a deep analysis of the stability within the calculation of phonon spectra and elastic constants as well as Gibbs energy. The electronic and magnetic properties show that the investigated compound is a half-metallic ferromagnetic material. We show that IrFeSi has an integer magnetic moment of 3${\mu }_B$ in good agreement with the Slater–Pauling (SP) rule. By means of the Boltzman theory, we find that the investigated compound exhibits an interesting thermoelectric performance at room temperature.

We studied the dissipation effect induced by the internal relative motion between two nonlinear $\sigma$-models (NLSMs). The internal degrees of freedom (DOF) of the two NLSMs coupled to each other via an interface potential. We performed the path integral of the vacuum persistence amplitude (VPA) and got the quantum action. Then we introduced the relative motion via a boost transformation with velocity parameter $v=|v|$. Furthermore, we calculated the imaginary part of the boosted quantum action which was proportional to the vacuum decay probability. At last, we calculated the frictional force. The numerical results gave the velocity $v$ dependency of the vacuum decay probability, and the velocity $v$ dependency of the frictional force. There was a threshold of relative velocity $v$ for the vacuum decay probability and the frictional force. We gave a classical argument of the existence of the threshold, and the argument matched the mathematical results.

In the recent past, exploiting nonvolatile memory devices to facilitate in-memory computation benchmarks has demonstrated a considerable capability to address the von-Neumann drawbacks. This process resulted in a tremendous effort towards spintronics memory development. Due to the voltage-controlled magnetic anisotropy (VCMA) effect, the toggle magnetoresistive random-access memory (MRAM) exhibits faster switching and lower power consumption than spin-transfer torque (STT) MRAM. We assessed read/write access time, magnetized time and anisotropic field for crystalline perpendicular magnetic tunnel junctions (CPMTJ) with detailed material study and device parameters in this work. These junctions are affected by the VCMA effect. Various VCMA parameters, including the VCMA coefficient, the time constant and antiparallel (AP) resistance on the saturated magnetization, are measured via the memory cell’s SPICE modeling. The Rashba spin–orbit interaction (SOI) and spin-valve model are developed by MATLAB scripting for evaluating a Rashba and Hamiltonian vector field. The toggle spin torque (TST) in the TST-MRAM cell is generated due to the interconnection between STT and spin–orbit torque (SOT) mechanisms. The TST-MRAM cell’s benefits are energy efficiency, large TMR ratio and superfast read and write operation. This work’s novel part is that the Hamiltonian field can control the net magnetization factor by the Rashba SOI effect. We end this paper with the performance enhancement techniques of MRAM cells due to VCMA and Rashba SOI effect.

In this paper, we propose a one band tight binding model Hamiltonian for the newly discovered 122-type Selenide family of the iron-based system incorporated with the nearest-neighbor (NN) and the next-nearest-neighbor (NNN) hopping integrals $t_1$ and $t_2$, respectively. The spin–spin interactions of the electrons leading to the antiferromagnetic spin density wave (SDW) order have been studied at wave vector $Q=(\pi ,\pi ∕2)$. The electron Green’s functions are calculated from the Hamiltonian model using Green’s function technique and finally the SDW gap equation is derived and studied using their NN and NNN spin coupling $g_1$ and $g_2$, respectively.

Magnetic nanotubes are a new material platform to realize the spin-dependent Seebeck effect (SDSE) and thermal spin-filtering effect (TSFE) in spin caloritronics. Here, we designed several magnetic nanotubes using triangular graphene-flake-doped boron nitride nanotubes (GFBNNTs) and found that the band structure of these GFBNNTs can be effectively engineered by embedding graphene flakes (GFs) of different sizes. The magnetic boron nitride nanotubes (BNNTs) ((5, 5)-6N) generate a good SDSE with nearly symmetric spin-up and spin-down currents, while the magnetic BNNTs ((10, 0)-6N) generate a good TSFE. These theoretical results about the SDSE and TSFE in nanotubes enrich the spin caloritronics and suggest material candidates to realize the SDSE and other inspiring thermospin phenomena.