SPIN

The Monte Carlo studies presented in this paper provide insight into stable phases, magnetic hysteresis cycles and magnetization plateaus in mixed nano-Kagome bilayer lattices. In particular, exchange coupling reduction affects coercive and saturation fields, and temperature variations impact hysteresis loop regions. The role of the crystal field in the design of magnetization plateaus was highlighted. The study explores the interaction of magnetization plates and their response to critical and saturation fields, depending on the crystal field and ferrielectric coupling. Extremely low temperatures ($T=0.01$) play a crucial role in the manifestation of magnetization plateaus. These results suggest possible applications in nanotechnology, particularly in the design of storage media.

Some physical properties (structural, dielectric and optical) of a complex lead-free ceramic [${\text{Bi}}_{1∕2}$${\text{Na}}_{1∕2}$][${\text{Fe}}_{1∕2}$${\text{W}}_{1∕2}$]O₃ have been thoroughly examined in different experimental conditions in this study. It was fabricated via a solid-state reaction method. The crystal structure is monoclinic, according to the detailed analysis of the X-ray diffraction pattern. Also, the functional vibrational bands can be observed in the FT-IR and Raman spectra, which support the creation of the molecular structure. Scanning electron microscope (SEM) images of the sample clearly show the effects of ${\text{Na}}^{+}$ and ${\text{W}}^{6+}$ incorporation in morphology, and energy dispersive X-ray spectroscopy (EDX) indicates the existence of all constituents. The non-overlapping small polaron tunneling (NSPT) and correlated barrier hopping (CBH) model conduction mechanisms are examined through Jonscher’s power law. The contribution of the grain and grain boundary to the capacitive behavior is shown by Nyquist plots. According to a leakage current analysis, the compound exhibits Ohmic and space charge limited conduction (SCLC) conduction mechanisms. Electric field polarization was used to study the ferroelectric nature. The findings of this study show that the inclusion of ${\text{Na}}^{+}$ and ${\text{W}}^{6+}$ is an efficient technique to improve its dielectric and optical characteristics.

This study offers a comprehensive investigation into the fabrication of all-oxide-based magnetic tunnel junctions (MTJs) utilizing the focused ion beam (FIB) nanomachining method. The oxide thin films of SrTiO₃ (STO), La${}_{1-x}$Ca_xMnO₃ (LCMO) and La${}_{1-x}$Sr_xMnO₃ (LSMO) were grown using pulsed laser deposition (PLD). Magnetization measurements at 5K revealed a notable difference in coercivity between LCMO and LSMO films, highlighting their suitability as electrodes in MTJ device fabrication. The deposited trilayer structure of LCMO/STO/LSMO exhibited heteroepitaxial growth, enabling the independent magnetic switching of electrode layers in the MTJ with the STO barrier layer. Conventional photolithography and ion milling were used to create a series of 4$\mu$m Hall bar tracks in the deposited films. Nanopillar devices, sized 250nm×250nm, were successfully fabricated on these 4$\mu$m tracks by optimizing the FIB nanomachining technique. The fabricated MTJs demonstrated a high tunnel magnetoresistance (TMR) response, leading to the conclusion that the FIB nanomachining technique holds significant promise for the development of high-performance oxide-based spintronic devices.

This study focuses on examining magnetic property performances among three nano-Heusler Ru₂MnX alloys (where X is replaced by the atoms V, Ta and Nb). The investigation was conducted through Monte Carlo simulations, exploring the magnetic properties of these alloys. The study established a clear transition from ferrimagnetic to superparamagnetic behavior. Furthermore, it exposed the effects of magnetization in each nano-Heusler alloy relative to physical factors.

This study used Monte Carlo analysis to investigate how edge vacancies impact magnetic behavior in graphene-like nanostructures. The quantity and presence of edge vacancies intricately affected the magnetic response of the system. Moreover, the system displays an increased sensitivity to changes in coupling interaction and external magnetic field. This sensitivity may be due to the low number of atoms in the system. Furthermore, the hysteresis cycle area behavior was found to be influenced by both the temperature and the number of atoms in the system. The tunability and sensitivity of edge vacancies in graphene-like nanostructures hold great promise for innovations and advancements in nanotechnology.

Electric currents passing through ferromagnets can impact the magnetization dynamics via the so-called spin-transfer torque (STT) effect. In this paper, we present a theoretical study on the current influence on magnonic activity, a recently reported spin wave (SW) chiral effect in ferromagnetic nanotubes. By micromagnetic simulations, we show that an electric current can cause a significant change in the rotatory power of the SW modes propagating in a longitudinally magnetized nanotube. This result is well explained by using the Fresnel model in optics assuming a SW circular birefringence. An analytical method is developed to solve the first-order mode, yielding perfect agreements with the numerical results. Our results provide a new approach to manipulate the SW propagating properties in ferromagnetic nanocylinders.

The molecular approach of a spin model is constructed on the Bethe lattice (BL), and then it is examined in terms of exact recursion relations. Rather than assuming that each BL site is inhabited by a single spin, each site is occupied by two spin-1/2 atoms A and B, forming a molecule. Each molecule is considered to contain two spin-1/2 atoms, as well as $q=3,4,$ or 6 nearest-neighbor molecules. In addition to the internal interactions between the atoms of each molecule, the molecules interact via their atoms in terms of bilinear interaction parameters J. Atoms of a molecule interact with $J_{A^i{B}^i}$, while the molecules interact via their atoms in terms of $J_{A^i{B}^{i+1}}=J_{B^i{A}^{i+1}}$ and $J_{A^i{A}^{i+1}}=J_{B^i{B}^{i+1}}$. After obtaining the magnetizations of each atom in the central molecule of the BL, the average magnetization of the molecule is determined. It is found that the model presents first-and second-order and random phase transitions. The model also displays tricritical, bicritical and end points, in addition to reentrant behavior for appropriate J values.

We use the bond mean field theory, which is based on the Jordan–Wigner fermionization, to investigate the quantum critical behavior of a system composed of two-coupled Heisenberg Spin-$1/2$ two-leg ladders in the presence of an applied magnetic field. By examining the dependence of the ground state on the magnetic field for different coupling constants, we investigate the field-induced quantum criticality. The magnetization exhibits distinct plateaus: a zero magnetization plateau for fields below a threshold value of the field $h_{c1}$ and a saturation plateau for fields exceeding a second critical value $h_{c2}$. The spin bond parameters are calculated and found to show a critical behavior at $h_{c2}$.

We attempt to study the mixed-spin Ising on two decorated ferrimagnetic ternary metallic nanoislands possessing hexagonal and square structures, with a mixture of spin numbers 3/2, 1, and 1/2. Via the finite cluster approximation, the critical and compensation characteristics have been explored by implementing the influences of decorating and interface exchange couplings ($J_1$, $J_2$), along with the crystal fields ($D_{\sigma }$, $D_S$) on the phase diagrams and magnetizations. In the absence of crystal fields, the hexagonal structure exhibits only the second-order transition with one or two compensation points; meanwhile, the square structure undergoes the multiple transitions behavior (two or three transition temperatures) with a first-order transition at low temperatures. The inclusion of the crystal fields demonstrates the elevation of the ferrimagnetic region of order. Interestingly, we have uncovered under only the effect of $D_S$ acting on spin-1 sublattice the occurrence of the first-order with reentrance indicating two and three transitions for the hexagonal and square structures, respectively. Finally, under a uniform crystal field ($D_{\sigma }=D_S=D$), the first-order keeps existing only for the square nanoisland.

The electrical excitation of spin dynamics in antiferromagnets is important for the development of high-speed spintronic devices with a low power consumption. Here, we present a theoretical study of the spin dynamics generated in the Ni/Cu/Mn₂Au/Cu/Ni nanostructure by a perpendicular-to-plane electric current. Our investigation includes atomistic simulations of spin reorientations in a few monolayer antiferromagnetic Mn₂Au film and numerical calculations of nonequilibrium spin accumulation in the nanostructure comprising ferromagnetic Ni polarizers with antiparallel magnetizations. This combined approach enables us to quantify the dynamics of Mn magnetic moments induced by the spin-transfer torque created by the spin-polarized charge flow. The calculations show that the direct electric current with the density exceeding some temperature-dependent threshold value gives rise to steady-state auto-oscillations of the Néel vector in the $(001)$-oriented Mn₂Au nanolayer. As the precession of Mn magnetic moments occurs around an out-of-plane direction strongly deflected from their initial in-plane orientations, the emergence of auto-oscillations should be regarded as the realization of a dynamic spin reorientation transition in the antiferromagnetic crystal. Remarkably, the precession frequency rises with increasing current density J and exceeds 1THz at $J\approx 1.4\times 10^{13}$Am${}^{-2}$, which makes the described antiferromagnetic spin transfer nano-oscillator attractive for device applications. Furthermore, our simulations demonstrate that a picosecond current pulse injected into the Ni/Cu/Mn₂Au/Cu/Ni nanostructure can induce a precessional switching of the Néel vector. Depending on the current density and pulse duration, the Néel vector rotates by either 90° or 180° and attains stable orientation along the corresponding $〈110〉$ easy axis in the plane of the Mn₂Au nanolayer. This feature shows that the Ni/Cu/Mn₂Au/Cu/Ni nanostructure could be used as a nonvolatile memory cell with the electrical writing and readout.

Magnetic texture in a chiral material is touted as one of the next-generation nonvolatile computing elements. Thermal manipulation of magnetic textures attracts considerable attention and has promising applications. Here, the temperature-dependent magnetic properties of Ta/CoFeB/MgO thin film are studied experimentally and theoretically. We report the controllable spin texture distribution with a temperature gradient in the Ta/CoFeB/MgO thin film. The nucleation area could be generated at a certain location through the cooperation of heat and magnetic field. This method offers a way to realize spin texture injection at specific positions in magnetic thin films and devices. This work provides useful guidelines for the thermal control of the spintronic device operation.