Mixed Spin Research Articles

Critical and Compensation Behaviors of a Ferrimagnetic Multilayer System

By the use of Monte Carlo simulation, we have investigated the phase diagrams and magnetic properties of a ferrimagnetic Ising multilayer system with mixed spins (1, [Formula: see text]). The ground-state phase diagrams are first constructed for [Formula: see text]. To examine the influences of certain physical parameters of the system, namely the exchange interactions, the number of layers and the crystal field, we have studied the thermal behavior of the system magnetizations and the corresponding phase diagrams. The results obtained in this work show the existence of second- and first-order phase transitions and compensation temperatures. Moreover, we have investigated the hysteresis behavior, where the multi-loop phenomena are observed.

Quantitative behavior of (1,1/2)-MSIM on a Cayley tree

In this paper, using the self-similarity technique, we establish the Gibbs measures related to the Ising model having mixed spin (1,1/2) (shortly, (1,1/2)-MSIM) on the semi-infinite Cayley tree (CT) and rigorously investigate the phase transition phenomena for (1,1/2)-MSIM on the CT by looking at the non-uniqueness of the fixed points for the relevant dynamic system. We demonstrate that the model displays chaotic behavior in some regions via the Lyapunov exponent. We compute the thermal average spin for the model. We present some exact formulas to calculate the free energy and entropy associated with (1,1/2)-MSIM on the second-order CT by employing the cavity technique.

Periodic ground states for the mixed spin ising model with competing interactions on a Cayley tree

Periodic ground states for the mixed spin ising model with competing interactions on a Cayley tree

High-performance strategies for the recent MRSF-TDDFT in GAMESS.

Multiple ERI (Electron Repulsion Integral) tensor contractions (METC) with several matrices are ubiquitous in quantum chemistry. In response theories, the contraction operation, rather than ERI computations, can be the major bottleneck, as its computational demands are proportional to the multiplicatively combined contributions of the number of excited states and the kernel pre-factors. This paper presents several high-performance strategies for METC. Optimal approaches involve either the data layout reformations of interim density and Fock matrices, the introduction of intermediate ERI quartet buffer, and loop-reordering optimization for a higher cache hit rate. The combined strategies remarkably improve the performance of the MRSF (mixed reference spin flip)-TDDFT (time-dependent density functional theory) by nearly 300%. The results of this study are not limited to the MRSF-TDDFT method and can be applied to other METC scenarios.

Quantum coherence versus quantum-memory-assisted entropic uncertainty relation in a mixed spin-(1/2,1) Heisenberg dimer

Quantum coherence versus quantum-memory-assisted entropic uncertainty relation in a mixed spin-(1/2,1) Heisenberg dimer

The Influence of the Substrate on the Functionality of Spin Crossover Molecular Materials.

Spin crossover complexes are a route toward designing molecular devices with a facile readout due to the change in conductance that accompanies the change in spin state. Because substrate effects are important for any molecular device, there are increased efforts to characterize the influence of the substrate on the spin state transition. Several classes of spin crossover molecules deposited on different types of surface, including metallic and non-metallic substrates, are comprehensively reviewed here. While some non-metallic substrates like graphite seem to be promising from experimental measurements, theoretical and experimental studies indicate that 2D semiconductor surfaces will have minimum interaction with spin crossover molecules. Most metallic substrates, such as Au and Cu, tend to suppress changes in spin state and affect the spin state switching process due to the interaction at the molecule-substrate interface that lock spin crossover molecules in a particular spin state or mixed spin state. Of course, the influence of the substrate on a spin crossover thin film depends on the molecular film thickness and perhaps the method used to deposit the molecular film.

The energy spectrum and low-temperature magnetic properties of the decorated two-leg mixed spin ladder

The energy spectra and low-temperature magnetic properties of two one-dimensional Heisenberg mixed spin (s = 1, 1/2) systems, namely decorated two-leg mixed spin ladders with the lattice topology of polyacene, are studied. The gapless character of the exact excitation energy spectra for both ladder models has been determined. We found numerically that the model with macroscopic ground state spin S0 has gapped excitations with the spin S > S0. This leads to the appearance of an intermediate plateau in field dependence of magnetization at low temperatures. We have shown that the ladder with equal coupling in legs has the maximal size of this plateau at the same coupling in rungs. For a mixed spin ladder model with Ising interactions in legs, the appearance of two intermediate magnetization plateaus at low temperatures and some values of coupling parameters was shown.

Hybrid magnonics in hybrid perovskite antiferromagnets

Hybrid magnonic systems are a newcomer for pursuing coherent information processing owing to their rich quantum engineering functionalities. One prototypical example is hybrid magnonics in antiferromagnets with an easy-plane anisotropy that resembles a quantum-mechanically mixed two-level spin system through the coupling of acoustic and optical magnons. Generally, the coupling between these orthogonal modes is forbidden due to their opposite parity. Here we show that the Dzyaloshinskii–Moriya-Interaction (DMI), a chiral antisymmetric interaction that occurs in magnetic systems with low symmetry, can lift this restriction. We report that layered hybrid perovskite antiferromagnets with an interlayer DMI can lead to a strong intrinsic magnon-magnon coupling strength up to 0.24 GHz, which is four times greater than the dissipation rates of the acoustic/optical modes. Our work shows that the DMI in these hybrid antiferromagnets holds promise for leveraging magnon-magnon coupling by harnessing symmetry breaking in a highly tunable, solution-processable layered magnetic platform.

Compensation temperature and hysteresis behaviors of a graphene-like bilayer: Monte Carlo Study

Using the Monte Carlo method, the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters such as crystal field, exchange coupling, external magnetic field, and temperature. The variations of magnetization, magnetic susceptibility, specific heat, and internal energy with the change of temperature are discussed. In addition, we also plot the phase diagrams including transition temperature and compensation temperature. Finally, multiple hysteresis loops under certain parameters are given.

Magnetic Behavior of Ising Nanowire with Mixed Integer Spins: A Monte Carlo Study

The magnetic and thermal properties of a ferrimagnetic mixed spin-1 and spin-2 cubic Ising nanowire are studied by using the Monte Carlo simulation. The influences of the nearest (JAB) and next-nearest neighbor (JA and JB) exchange interactions and the single-ion anisotropies (DA and DB) on the critical and compensation temperatures are illustrated. Moreover, the phase diagrams on the (temperature, anisotropy) plane are plotted for several values of JA/|JAB|. The system shows very rich and interesting behaviors, namely first and second order phase transitions, tricritical points and compensation phenomenon. Finally, the dependence of hysteresis loops on the anisotropies, the exchange interactions and the temperature is also investigated.

Crystal and External Magnetic Fields induced Compensation Temperatures in a Decorated Mixed Spin Ferrimagnet

Crystal and External Magnetic Fields induced Compensation Temperatures in a Decorated Mixed Spin Ferrimagnet

Study of magnetocaloric effect and magnetic properties of the nano-graphene bilayer with RKKY interactions of a mixed spins S = 3/2 and σ = 3: a Monte Carlo simulation

Study of magnetocaloric effect and magnetic properties of the nano-graphene bilayer with RKKY interactions of a mixed spins S = 3/2 and σ = 3: a Monte Carlo simulation

Study of Magnetic and Magnetocaloric Properties of the Nano‐Graphene of Mixed Spins S = 3/2 and σ = 2: A Monte Carlo Simulation

The magnetic and magnetocaloric properties of the nano‐graphene monolayer structure consisting of mixed spins S = 3/2 and σ = 2 are studied by using Monte Carlo simulations. The ground‐state phase diagrams corresponding to several physical parameters are first discussed. The influence of the number of lattice sites on the total and partial magnetizations and the magnetic susceptibilities has been investigated. The critical temperature is deduced. The effect of exchange interaction, external magnetic, and crystal field on total magnetizations is studied. Magnetic hysteresis cycles are obtained. Specific heat change and magnetic entropy changes are inferred for several magnetic fields. Finally, the relative cooling power is determined.

The $$\pm J$$ distribution in the mixed spin-$$1/2$$ and $$5/2$$ Blume–Capel model

The $$\pm J$$ distribution in the mixed spin-$$1/2$$ and $$5/2$$ Blume–Capel model

The $\pm J$ distribution in the mixed spin-$1/2$ and $5/2$ Blume-Capel model

Рассмотрена модель Блюма-Капеля со смесью спинов $1/2$ и $5/2$ на решетке Бете, в которой константа связи $J$ имеет вероятностное распределение и принимает значения $J>0$ и $J<0$ с вероятностями $p$ и $1-p$, с параметром настройки $\alpha$. Для этой модели получены фазовые диаграммы на плоскостях $(\alpha,T)$ и $(p,T)$ при $0\leq p\leq 1$ и $0\leq\alpha\leq 1$ для заданных значений параметра $D$ одноионной анизотропии. Фазовые диаграммы строятся путем анализа термических вариаций параметров порядка с помощью точных рекуррентных соотношений с последующим введением в модель вероятностного распределения. В случае координационного числа $q=3$, соответствующего сотообразной решетке, в этой модели в дополнение к тройным и двойным критическим точкам наблюдаются фазовые переходы первого и второго рода.

Phase diagram and thermoelastic property of iron oxyhydroxide across the spin crossover under extreme conditions

Spin transition and its effect on the physical properties of iron-bearing minerals at high pressure-temperature $(P\text{\ensuremath{-}}T)$ are of great importance for understanding the structural heterogeneity of Earth's mantle. Here, we investigate the phase diagram and thermoelastic properties of iron oxyhydroxide (FeOOH) across the spin crossover using dynamic high $P\text{\ensuremath{-}}T$ experiments and theoretical simulations. The Hugoniot equation of state in FeOOH has been measured up to $\ensuremath{\sim}90$ GPa and $\ensuremath{\sim}2100$ K in a two-stage light-gas gun and exhibits a density discontinuity between 47 GPa (\ensuremath{\sim}950 K) and 61 GPa (\ensuremath{\sim}1150 K) due to the high-low spin transition of ${\mathrm{Fe}}^{3+}$, which is consistent with our first-principles calculations. The $P\text{\ensuremath{-}}T$ phase diagram indicates that the shock-elevated temperature shifts the spin transition to a higher pressure and broadens the pressure range of mixed spins. The large volume collapse of FeOOH during its spin crossover leads to remarkable elastic anomalies, with \ensuremath{\sim}60% softening of adiabatic bulk modulus and a negative Poisson's ratio (\ensuremath{-}0.1) of abnormal auxeticity in the mixed-spin phase. Our results suggest that FeOOH undergoes an unselective spin transition of ferric iron at the corresponding $P\text{\ensuremath{-}}T$ conditions of the Earth's 1400--1800 km depth and exhibits drastic softening in sound velocities and elastic modulus which may be detected as seismic heterogeneities in subducting slabs of the lower mantle.

Thermodynamic behaviors and hysteresis loops of an edge-modified Kekulene monolayer: A Monte Carlo study

We studied the magnetic and thermodynamic behaviors of an edge-modified Kekulene monolayer using the Monte Carlo method and established the Ising model with the mixed spins of 2 and 5/2. The function curves of temperature on magnetization, susceptibility, internal energy, and specific heat induced by various physical parameters are discussed respectively. The relationship between blocking temperature and various physical parameters is obtained. We also clarify the role of crystal field, exchange coupling and temperature on the hysteresis loops.

The classification of disordered phases of mixed spin (2,1/2) Ising model and the chaoticity of the corresponding dynamical system

We study an Ising model having the mixed spins {±1/2} and {±2,±1,0} on Cayley tree of second-order. We construct the Gibbs measures corresponding to the model and classify the disordered phases associated to the Gibbs measures. Using the compatibility condition, we obtain the system of functional equations associated with the model. Contrary to the Ising model with two different neighbor interactions, we prove that for the given model, the phase transition phenomenon occurs in both the antiferromagnetic and antiferromagnetic regions. Stability analysis of the dynamic system associated with the model is performed at the obtained fixed point. By calculating the Lyapunov exponent numerically, we show that the corresponding dynamical system exhibits the chaotic behavior in some regions. We identify regions where the disordered phases are extreme by means of a tree-indexed Markov chain. We satisfy the Kesten–Stigum condition for non-extremality of the disordered phase according to the fixed point.

Magnetocaloric properties and hysteresis loops of hexagons in a square–hexagon-octagon (4-6-8) structure with mixed spins: Monte Carlo study

In this work, we have studied the magnetocaloric properties of a 1, 3/2 and 5/2 mixed spin model on a square–hexagon-octagon (4-6-8) structure, investigated by Monte Carlo simulations. The total magnetization and the magnetization of each sub-lattice of the mixed-spin lattice have been analyzed. We investigated the effects of the external magnetic field, the exchange coupling interactions and the temperature in order to explicit the magnetic properties of these structure systems. The magnetic susceptibility and heat specific were determined. The magnetic spin-reorientation transition and ferrimagnetic-paramagnetic transitions were found, along with the magnetic entropy changes. Finally, the hysteresis loops under the effect of exchange interactions, temperatures and the crystal fields have been discussed.

Quantum coherence and mutual information of mixed spin-(1/2, 5/2) Ising-<i>XXZ</i> model on quasi-one-dimensional lattices

The mixed spin-(1/2, 5/2) Ising-<i>XXZ</i> model on quasi-one-dimensional lattices can be used to study the properties of some materials (such as heterotrimetallic Fe-Mn-Cu coordination polymer), and the study on this model is beneficial to the practical applications of such materials in the field of quantum information. The quantum coherence and mutual information are calculated by the transfer matrix method, and the effects of Ising interaction, temperature and magnetic field on them are discussed. The results show that the quantum coherence decreases gradually with the increase of Ising interaction at extremely low temperatures, while there is one minimum value of mutual information in an isotropic system and there appear four minimum values in an anisotropic <inline-formula><tex-math id="M3">\begin{document}$\left( {\varDelta = 4} \right)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20230381_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20230381_M3.png"/></alternatives></inline-formula> system. Furthermore, quantum coherence and mutual information jump abruptly at quantum phase transition points where the first derivatives of them exhibit singular behaviors. The quantum coherence and mutual information at finite temperatures are also studied. As the temperature increases, they decrease monotonically in a weak magnetic field, but they first increase and then decrease in a higher magnetic field, which is caused by the competition between thermal fluctuation and magnetic field. Compared with quantum mutual information, quantum coherence exists over a wider range of magnetic field and temperature, which can be easily manipulated experimentally.