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An upsurge of research activities is conducted to assess the magnetic properties of graphene nanoribbons with a keen focus on spintronic applications. The critical and compensation characteristics of mixed spin-3/2 and spin-1/2 Ising nanoribbons (Nrbs) with rectangular and hexagonal shapes under a transverse field are explored employing the finite cluster approximation. In the absence of transverse fields, only the rectangular Nrb, may exhibit one or two compensation points. This compensation persists under a transverse field Ωσ that exclusively affects the spin-1/2 of the σ-sublattice, where the order is destroyed at some Jσ-dependent critical transverse fields at T = 0. Interestingly, the insertion of a transverse field ΩS acting only on the S-sublattice, demonstrates that the order cannot be destroyed at low temperatures, with the possibility of reentrance as well as tricritical behaviors for rectangular Nrb. Finally, all these behaviors have been confirmed through an analysis of the magnetizations. [ABSTRACT FROM AUTHOR]

In this paper, the compensation characteristics and hysteresis loops of a ferrimagnetic mixed-spin diluted fullerene-like (XY)540 are studied based on Monte Carlo method. We show the ground-state phase diagrams in order to explore the stable configuration states. The temperature dependence of magnetization, magnetic susceptibility, internal energy, specific heat, and entropy are presented. The phase diagram including compensation temperature Tcomp and phase change temperature Tc is obtained. The multi-loop hysteresis phenomena under the influence of diverse physical parameters are observed. Finally, the critical exponents of the fullerene-like (XY)540 are obtained. [ABSTRACT FROM AUTHOR]

Spin-crossover (SC) compounds are fascinating materials that exhibit colorful phase transitions induced by temperature, pressure, photoirradiation, etc. From the microscopic point of view, the electronic (spin) state of a molecule changes between the low-spin (LS) and high-spin (HS) states by such stimuli, and a variation of the molecular size follows through the vibronic coupling between the electronic state and structure in the molecule. This causes an elastic distortion and then an elastic interaction. The elastic interaction is essential in cooperative properties of SC phenomena. In this paper, we present a tutorial study on elastic interaction models for SC phenomena, which are the recent trend of modeling of SC compounds. We focus on multistep transitions, which are a topic of SC phenomena. We analyze the phase diagrams including the metastable phases for several SC systems, in which antiferromagnetic-like and ferrimagnetic-like phases are associated in addition to the LS and HS phases. Making use of the phase diagrams, we show various patterns of thermally induced SC transition with steps. We also investigate SC transitions with steps in a core-shell SC nanocomposite composed of two different SC compounds. We focus on two cases: the core has a lower transition temperature than the shell, and the core has a higher transition temperature. We show characteristic features of difference in the two systems. [ABSTRACT FROM AUTHOR]

In some materials exhibiting field-induced first-order transitions (FOTs), the equilibrium phase-transition line is hidden by the hysteresis region associated with the FOT. In general, phase diagrams form the basis for the study of material science, and the profiles of phase-transition lines separating different thermodynamic phases include comprehensive information about thermodynamic quantities, such as latent heat. However, in a field-induced FOT, the equilibrium phase-transition line cannot be precisely determined from measurements of resistivity, magnetization, etc, especially when the transition is accompanied by large hysteresis. Here, we demonstrate a thermodynamics-based method for determining the hidden equilibrium FOT line in a material exhibiting a field-induced FOT. This method is verified for the field-induced FOT between antiferromagnetic and ferrimagnetic states in magneto-electric compounds ( Fe 0.95 Zn 0.05 ) 2 Mo 3 O 8 . The equilibrium FOT line determined based on the Clausius–Clapeyron equation exhibits a reasonable profile in terms of the third law of thermodynamics, and it shows marked differences from the midpoints of the hysteresis region. Our findings highlight that for a field-induced FOT exhibiting large hysteresis, care should be taken for referring to the hysteresis midpoint line when discussing field-induced latent heat or magnetocaloric effects. [ABSTRACT FROM AUTHOR]

Band structure and topology of magneto-spin–orbit graphene is investigated using the proposed tight-binding model that incorporates both Rashba and sublattice-resolved collinear exchange couplings in a generic ferrimagnetic (FIM) setting for in-plane and out-of-plane magnetization directions. The resulting band structures were analyzed for possibilities to extract the strengths of exchange and Rashba couplings from experimental spin-resolved ARPES measurements of the valley gaps and π -state spin-splittings. It was shown that the topologically trivial in-plane FIM situation admits simple expressions for these quantities, whereas the out-of-plane FIM, which admits a nontrivial band topology, is harder to analyze. The obtained topological phase diagrams for the out-of-plane FIM case show that the anomalous Hall conductance is quite stable with respect to the antiferromagnetic (AFM) interaction, which tends to interfere with the QAHE phase; moreover, the topological phase transition has a rather smooth character with respect to the AFM coupling strength. [ABSTRACT FROM AUTHOR]

The ferrimagnetic-ferromagnetic-ferrimagnetic quaternary alloy consisting of the spins S i A = 1 , S j B = 3 / 2 , S j C = 5 / 2 and S j D = 2 in the form of A B p C q D r with B, C and D being the possible nearest-neighbors of A with the probabilities p, q and r, respectively, is investigated in terms of the mean field theory (MFT) based on the Bogoliubov inequality for free energy. The thermal behaviors of magnetizations belonging to the individual spins and total magnetization are examined in detail to map the possible phase diagrams on various planes. It was found that the model only exhibits second-order phase transitions in addition to one compensation temperature for appropriate values of the system parameters. In order to support the existence of the compensation temperatures, we have also carried out the Monte Carlo (MC) simulations and an agreement was shown with the predicted result of the MFT approach. We have also analyzed the effects of the bilinear interaction parameter between type-A atoms J A A and the exchange interaction parameter ratio R = J A X / | J A B | ( J A X is the bilinear interaction parameter between type-A atoms and type-X atoms with X = C or D) on compensation temperatures. Our findings are compared to those reported in the literature and suitable agreements are observed. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are meta-stable spin structures that naturally emerge in magnetic materials. While a vast amount of effort has gone into the study of their properties, their counterpart of opposite topological charge, the anti-skyrmion, has not received as much attention. We aim to close this gap by deploying Monte Carlo simulations of spin-lattice systems in order to investigate which interactions support anti-skyrmions, as well as skyrmions of Bloch and Néel type. We find that the combination of ferromagnetic exchange and Dzyaloshinskii–Moriya (DM) interactions is able to stabilize each of the three types, depending on the specific structure of the DM interactions. Considering a three-dimensional spin lattice model, we provide a finite-temperature phase diagram featuring a stable anti-skyrmion lattice phase for a large range of temperatures. In addition, we also shed light on the creation and annihilation processes of these anti-skyrmion tubes and study the effects of the DM interaction strength on their typical size. [ABSTRACT FROM AUTHOR]

We investigated the dynamic phase transitions (DPTs) in the mixed spin (2, 5/2) Blume-Emery-Griffiths model with repulsive biquadratic interaction in the presence of a time-varying magnetic field. We used the path probability method to obtain the set of the dynamic equations. We numerically solved these dynamic equations to characterize the nature of first- and second-order phase transitions and to find the DPT temperatures as well as obtain the phases in the system. We constructed the dynamic phase diagrams (DPDs) in reduced temperature and amplitude of oscillating magnetic field plane. We observed that the DPDs display richer, complex and more topological various type of phase diagrams. In particular, DPDs exhibit the disordered phase, antiquadrupolar or staggered phase, six different ferrimagnetic phases, three different nonmagnetic phases, and numerous mixed phases. DPDs also display two dynamic tricritical points for only smaller values of crystal-field interactions, multiple critical end and double critical end points, one zero-temperature critical point, one inverse critical end point, and a quadruple point depending on interaction parameters. The system always shows the reentrant behaviors for the higher values of magnetic field amplitude, but it does not exhibit the dynamic tricritical behavior for higher values of crystal-field parameter. [ABSTRACT FROM AUTHOR]

CaCu3Fe4O12 exhibits a temperature-induced transition from a ferrimagnetic-insulating phase, in which Fe appears charge disproportionated, as Fe 3 + and Fe 5 + , to a paramagnetic-metallic phase at temperatures above 210 K, with Fe 4 + present. To describe it, we propose a microscopic effective model with two interpenetrating sublattices of Fe ( 4 − δ ) + + and Fe ( 4 + δ ) + + , respectively, δ being a measure of the Fe-charge disproportionation. We include all 3d-Fe orbitals: t 2 g localized orbitals, with spin 3/2 and magnetically coupled, plus two degenerate itinerant eg orbitals with local and nearest-neighbor (NN) electron correlations, and hopping between NN eg orbitals of the same symmetry. Allub and Alascio [J. Phys.: Condens. Matter 24(49), 495601 (2012)] previously proposed a model to describe the phase transition in LaCu3Fe4O12 from a paramagnetic-metal to an antiferromagnetic-insulator, induced by temperature or pressure, involving charge transfer between Fe and Cu ions, in contrast to Fe-charge disproportionation. With the model proposed for CaCu3Fe4O12, modified to account for this difference between the two compounds, the density of states of the itinerant Fe orbitals was obtained, using Green's function methods. The phase diagram of CaCu3Fe4O12 was calculated, including phases exhibiting Fe-charge disproportionation, where the two eg orbitals in each site are symmetrically occupied, as well as novel phases exhibiting local orbital selectivity/asymmetric occupation of eg orbitals. Both kinds of phases may exhibit paramagnetism and ferromagnetism. We determined the model parameters which best describe the phase transition observed in CaCu3Fe4O12 and found other phases in different parameter ranges, which might be relevant for other compounds of the ACu3Fe4O12 family, presenting Fe-charge disproportionation and intersite charge transfer Fe-Cu. [ABSTRACT FROM AUTHOR]

The ferri-ferro-ferrimagnetic quaternary alloy described in the form as A B p C q D r consisting of spins S i A = 1 , S i B = 1 / 2 , S j C = 3 / 2 and S j D = 5 / 2 , respectively, is investigated in detail by the mean field theory (MFT) based on the Bogoliubov inequality for the free energy with the coordination number z = 3 . The phase diagrams are mapped on the planes of (R 1 = J AC / | J AB | , k T c / | J AB |) , (R 2 = | J AD | / | J AB | , k T c / | J AB |) , (p , k T c / | J AB |) and (r , k T c / | J AB |) by studying the thermal variations of the order parameters, i.e., the magnetizations. In addition to the critical temperatures, either second- or first-order phase transition temperatures without distinction, shown by the model, it also exhibits a single or a double compensation temperatures for appropriate values of the system parameters. The Monte Carlo (MC) simulations are also used to confirm the existence of the multi-compensation behaviors in the model as found by the MFT approach by examining the thermal variations of the total magnetization of the system. Our obtained results are compared to those reported in the literature, and reliable agreements are observed. [ABSTRACT FROM AUTHOR]

The mean-field approximation based on the Gibbs-Bogoliubov inequality and Monte Carlo simulations based on the Metropolis method in the Blume–Emery–Griffiths model were used to successfully examine a hexagonal Ising nanowire with spin-1. It was found that the model displays fascinating phase diagrams in various planes of interest by using both methods. The investigation of magnetic hysteresis cycles also exhibits interesting properties. The model not only presents first- and second-order phase transition lines, but also the tricritical and isolated critical points, multi-compensation temperatures, and magnetic hysteresis behavior with one to eight cycles. • The mean-field approximation based on the Gibbs-Bogoliubov inequality is applied. • The Monte Carlo simulations based on the Metropolis method is employed. • Spin-1 Blume–Emery–Griffiths model for hexagonal Ising nanowire is investigated. • First- and second-order transitions, tricritical and isolated critical points are found. • Multi-compensation and magnetic hysteresis with one to eight cycles are observed. [ABSTRACT FROM AUTHOR]

The magnetic properties of the mixed spin − 1/2 and spin − 1 Ising ferrimagnetic nanotube with a hexagonal lattice in the presence of the crystal field are investigated by means of the finite cluster approximation. We examine the effects of the crystal field, the surface shell, and core coupling parameters where the main attention has been paid to study the magnetizations and also the phase diagrams for both transition and compensation temperatures. In the absence of the crystal field, the compensation behavior exists only in a limited range of surface shell and core couplings. By introducing a crystal field, the compensation behavior is maintained and the tricritical behavior occurs depending on the strength of surface shell coupling. [ABSTRACT FROM AUTHOR]

A spin-1/2, Ising trilayered ferrimagnetic system on square Bravais lattice is studied, employing Monte-Carlo simulation with the single spin-flip Metropolis algorithm. The bulk of such a system is formed by three layers, each of which is composed entirely either by A or B type of atoms, resulting in two distinct compositions: ABA and AAB and two different types of magnetic interactions: ferromagnetic between like atoms and antiferromagnetic between unlike atoms. For such systems, Inverse Absolute of Reduced Residual Magnetisation is the absolute value of the ratio of the extremum of the magnetisation in between compensation and critical points and the saturation magnetisation. Variation of relative interaction strengths in the Hamiltonian, for a range of values, leads to the shift of compensation point and critical point and changes in the magnitude of inverse absolute of reduced residual magnetisation. Probable mathematical forms of dependences of the inverse absolute of reduced residual magnetisation and temperature interval between the critical and compensation temperatures on controlling parameters are proposed in the absence of applied magnetic field and have obtained phase diagrams for both types of configurations from these relations. This alternative description of the simulated systems may help technologists design magnetocaloric materials according to desired characteristics. [ABSTRACT FROM AUTHOR]

The phase diagram and the thermal variations of magnetizations in a graphene-like Ising nanoparticle decorated with spin-1 atom are examined by the effective-field theory with correlations. The effects of single-ion anisotropy of spin-1 atom to the magnetic properties are discussed. The following facts are clarified, when the appropriate conditions are satisfied: The transition temperature of the nanoparticle may become larger than that of bulk honeycomb lattice. The decorated nanoparticle exhibits many characteristic phenomena observed in bulk ferrimagnetic materials. [ABSTRACT FROM AUTHOR]

The hysteresis loops and compensation behaviors of a ferrimagnetic mixed system, consisting of two sublattices (A and B) with different spins (SA = 1 and SB = ½) and described by Heisenberg Hamiltonian on a cubic lattice, are investigated by using the pair approximation method. We have discussed the dependence of the compensation temperature on the D- crystal field interaction and J-exchange anisotropy. The influence of the longitudinal magnetic field and the magnetic hysteresis loops are also carried out. It is found that the model of mixed spin exhibits the possibility of two compensation points for several given sets of parameters. The model yields also second-order and first-order phase transitions, in addition to tricritical points. The reentrant phenomena can occur in some narrow ranges of D /|Jz| and Jxy /|Jz |. We have also observed the existence of triple hysteresis loop behaviors under the effects of special intrinsic parameters. [ABSTRACT FROM AUTHOR]

A mixed-spin (5/2, 3/2) Ising model is established to describe the antiferroelectric/ferroelectric (AFE/FE) BiFeO 3 /Co bilayer structure. We study the effects of the crystal field, exchange coupling and external longitudinal electric field on the dielectric properties of the bilayer based on Monte Carlo simulation. We illustrate the temperature dependence of polarization, susceptibility, internal energy and specific heat of the system in detail. As well, we depict the phase diagram and point out the rule of the blocking temperature with various parameters. In particular, we find rich and interesting multi-cycle electric hysteresis behaviors. The results show that these parameters play a crucial part in the physical properties of the AFE/FE BiFeO 3 /Co bilayer structure. [ABSTRACT FROM AUTHOR]

In this paper, the magnetic properties of a bi-layer nano-stanene like structure with RKKY (Ruderman-Kittel-Kasuya-Yoshida) interactions have been studied using Monte Carlo simulations. The considered system is composed of two magnetic planes with mixed spins σ = 7/2 and S = 1, separated by the non-magnetic planes (L). Firstly, the ground state phase diagrams for zero temperature are reported and discussed. Secondly, for non-zero temperature, we examine the effect of the RKKY interactions on the magnetic properties of our system. It is found that the value of the blocking temperature increases when decreasing the number of the non-magnetic layers. Furthermore, the effect of the exchange coupling interactions on the blocking temperature behavior are investigated. Finally, the effect of several physical parameters on the hysteresis cycles have been determined. [ABSTRACT FROM AUTHOR]

In this work, the phase transitions, for a molecular-based magnet, are examined using mean field method (MFM). The longitudinal magnetizations can be achieved by minimizing the free energy is an interesting function for locating and induction of spin compensation temperatures as well. By applying Blume-Capel (BC) configuration to a system consisting of two sublattices for a mixed spin-3/2 and spin-7/2on a square lattice in the anisotropies plane, the ground-state phase diagram of this system has been built. On principles of Bogoliubov inequality (BI) of the free energy, it has been investigated the spin compensation phenomena. In particular, characteristic ferrimagnetic features have been shown depending on an unequal crystal field parameters (DA, DB<-1.0) applied on the A−sites and B−sites, respectively. [ABSTRACT FROM AUTHOR]

The phase transitions of two mixed-spin (1/2,1) Ising nanoparticles with n = 4.0 and n = 6.0 are investigated by using the effective-field theory with correlations (EFT). The spin-1 atom with a single-ion anisotropy is decorated at the center of regular n-polygon (or nanoparticle with a value of n) and the spin-1/2 n atoms are put at the perimeter n sites. The phase transition in the nanoparticle with n = 6.0 is rather different from that in the nanoparticle with n = 4.0. It is shown that the number of n plays just like the coordination number z in the bulk mixed-spin Ising systems: the hexagonal nanoparticle with n = 6.0 has exhibited the first-order transition and the tricritical behavior, although the tetragonal nanoparticle with n = 3.0 did not show such behaviors, depending on the values of exchange interactions. [ABSTRACT FROM AUTHOR]

We investigate some critical phenomena of a Ising ferrimagnetic system on a square lattice with spins $Q=\pm 7/2, \pm 5/2, \pm 3/2$ , and ±1/2 in a $B$ sublattice and spins $S=\pm 5/2, \pm 3/2$ , and ±1/2 in a $A$ sublattice in presence of an $h'$ external magnetic field, such that $Q$ and $S$ are the nearest-neighbors ferrimagnetically coupled. Using Monte Carlo simulations, we calculate the finite-temperature phase diagrams of magnetization, specific heat, and magnetic susceptibility of the model. The system is defined by a Hamiltonian $(\mathcal {H})$ that contains ferromagnetic next-nearest-neighbors interactions between $S$ spins ($J'_{2}$), as well as external magnetic field and anisotropy interactions at each point of lattice. For a defined range of parameters in $\mathcal {H}$ , the system exhibits discontinuities in their physical variables and spin compensation behaviors. In the planes $J'_{2}-k_{\mathrm{ B}}T'$ and $h'-k_{\mathrm{ B}}T'$ , we analyze the relationship between the critical, compensation, and discontinuous phase transition temperatures with the external magnetic field and the next-nearest-neighbors interaction between $S$ spins. We found that the existence of discontinuous phase transition depends on the strengths of $h'$ and $J'_{2}$. [ABSTRACT FROM AUTHOR]

A group‐theoretical framework to describe vacancy ordering and magnetism in the Fe1−xS system is developed. This framework is used to determine the sequence of crystal structures consistent with the observed magnetic structures of troilite (FeS), and to determine the crystallographic nature of the low‐temperature Besnus transition in Fe0.875S. It is concluded that the Besnus transition is a magnetically driven transition characterized by the rotation of the moments out of the crystallographic plane to which they are confined above the transition, accompanied by small atomic displacements that lower the symmetry from monoclinic to triclinic at low temperatures. Based on the phase diagram, magnetically driven phase transitions at low temperatures are predicted in all the commensurate superstructures of pyrrhotite. Based on the phase diagram, magnetically driven spin reorientations at low temperatures are predicted in all the commensurate superstructures of pyrrhotite. The exact nature of the spin rotation is determined by the symmetry of the vacancy‐ordered state and based on this spin‐flop transitions in 3C and 5C pyrrhotite and a continuous rotation akin to that seen in 4C pyrrhotite are predicted. A Besnus‐type transition is also possible in 6C pyrrhotite. Furthermore, it is clarified that 3C and 4C pyrrhotite carry a ferrimagnetic moment whereas 5C and 6C are antiferromagnetic. [ABSTRACT FROM AUTHOR]

In this work, the Effective Field Theory (EFT) based on the probability distribution method is used to study the phase diagrams of an antiferroelectric nanowire with core/shell morphology, in the presence of a random transverse field. We have investigated the effects of the temperature, the concentration c , the surface and the interfacial couplings on the critical and the compensation behaviors (T c and T comp) of the system. The polarization, the susceptibility and the pyroelectric coefficient as a function of the temperature are examined. In addition, the phase diagrams of the nanowire are investigated in detail by modifying the system parameters. It is found that the interfacial coupling | J int / J c | shifts the random transverse field to higher values, therefore the area of the ordered phase is enlarged, which could affects the critical and the compensation temperatures. • The phase diagrams of a nanowire with antiferroelectric interfacial coupling are examined by the effective field theory. • The effect of the antiferromagnetic interfacial coupling on the critical and the compensation behaviors is studied. • The influence of the random transverse field on electric properties. • The dependence of the polarization, pyroelectric coefficient and susceptibility on the temperature are investigated. [ABSTRACT FROM AUTHOR]

• Ferrimagnetic mixed spin (3/2,1) Ising for zigzag and armchair graphene-like nanoribbons (GNRs) is investigated using the finite cluster approximation FCA. • Transition reentrance is revealed for both GNRs for lower J co strength. • Double compensation points are identified for the armchair GNR under the effect of the shell crystal field. • The core crystal field may lead for both zigzag and armchair GNRs, to a tricritical behavior. Graphene-like nanoribbon structures (GNRs) in which singular magnetic properties emerge because of the graphene-cutting process, may offer unique opportunities for future technological development such as spintronics. Using the finite cluster approximation, research has been implemented on some magnetic and critical characteristics of a mixed spin-3/2 and spin-1 Ising ferrimagnetic graphene-like nanoribbon with two typical edges, namely armchair, and zigzag. We investigate the influences of such aspects as crystal fields, exchange couplings, and temperature on phase diagrams and magnetizations. Tricritical as well as compensation behaviors have been demonstrated under the effect of the above physical parameters. In particular, only armchair GNR may exhibit double compensation points. Meanwhile, an unexpected reentrant transition has been discovered for both GNRs, which is mainly due to the finite size effect. [ABSTRACT FROM AUTHOR]

In this study, a bilayer Kagome lattice with RKKY interaction is described using a ferrimagnetic mixed spin-3/2 and spin-2 Ising model. Interesting compensation temperature and hysteresis loops of the system generated by various physical parameters, such as the crystal fields of sublattices (D a , D b), the interlayer exchange coupling (J R) and the intralayer exchange coupling (J b) are explored using Monte Carlo simulation. The results demonstrate that the compensation temperature (T comp), weaker D a and J b , and stronger D b , are favourable for the emergence of the compensation temperatures. Besides, under certain physical parameters, the system may exhibit triple-loop hysteresis behavior and multiple magnetization plateaus. • A ferrimagnetic mixed-spin (3/2, 2) Ising model on the bilayer Kagome lattice with RKKY interaction was proposed. • The effects of the crystal field, exchange coupling and non-magnetic layer were studied. • Magnetization, partial magnetization, and susceptibility were discussed. • Phase diagrams of the critical and compensation temperatures were obtained. • Interesting multi-loop hysteresis characteristics and magnetization plateaus were found. [ABSTRACT FROM AUTHOR]

In this paper, the ferrimagnetic mixed-spin (3/2, 5/2) Ising model was established to investigate the magnetic and thermodynamic properties of a nanoisland bilayer system with graphene-like structure by Monte Carlo simulation. We have analyzed the magnetization of the system and two sublattices, susceptibility, internal energy and hysteresis loops in detail. We have obtained the phase diagrams of the blocking temperature T B affected by the effects of various physical parameters. The triple hysteresis behavior has been observed, which originates from the competition among various physical parameters. Our results are comparable with those of other theoretical and experimental research. • The ferrimagnetic mixed-spin (3/2, 5/2) graphene-like nanoisland bilayer in the longitudinal magnetic field has been investigated. • Magnetization, susceptibility and internal energy have been discussed. • The phase diagrams of blocking temperature have been obtained under the influence of various physical parameters. • The triple hysteresis behavior have been found for certain physical parameters. [ABSTRACT FROM AUTHOR]

In this work, we study the magnetic properties of a borophene core-shell structure with spins σ = 5/2 and S = 3/2, using Monte Carlo simulations. We start by discussing the ground state phase diagrams corresponding to several physical parameters. Then the magnetizations and the susceptibilities have been analyzed. Besides, we explore the thermal magnetization behavior under the effect of the reduced exchange coupling interactions. Furthermore, we investigate the presence of the compensation temperature induced by the presence of a core shell structure and resulted from the variation of the reduced coefficient coupling. Finally, the variation of the total magnetizations as a function of the reduced exchange coupling interactions, the crystal and the external fields has been discussed. • Monte Carlo Simulations is used to investigate the magnetic properties of the core-shell Borophene. • The ground state phase diagrams are established. • The effect of exchange coupling interactions and magnetic external and crystal fields are analyzed. • The existence of compensation Temperature is studied. • The hysteresis cycles are explored. [ABSTRACT FROM AUTHOR]

Magnetic properties of a superlattice that consists of three square layers with Ising spins σ = 1 / 2 , s = 1 and q = 5 / 2 , are investigated by means of standard Monte Carlo simulations and Mean Field Theory. The Hamiltonian model comprises contributions of intralayer and interlayer exchange interactions and the applied external magnetic field. Effects of the external magnetic field on magnetic behaviors have been thoroughly studied in the presence of thermal excitation. Ground state and thermal phase diagrams are numerically computated by both methods. Ground state phase diagrams of the system exhibit one ferromagnetic phase (1/2, 1, 5/2) and three ferrimagnetic ones: (−1/2, 1, 5/2), (−1/2, −1, 5/2) and (−1/2, 1, −5/2). A number of interesting phase diagrams and phenomena have been found, including hysteresis behaviors. [ABSTRACT FROM AUTHOR]

We used mean-1eld theory based on the Bogoliubov inequality for the Gibbs free energy to examine the magnetic properties of a mixed spin-5/2 and spin-7/2 Blume-Capel ferrimagnetic system. The thermal behaviours of the system magnetization are classi1ed according to the extended Néel nomenclature. The system exhibits compensation phenomena where a complete cancellation of sublattice magnetizations is observed below the critical temperature. Temperature-dependent phase diagrams are constructed for the case of unequal sublattice crystal 1eld interactions. Under appropriate conditions, our calculations reveal 1rst-order transitions in addition to second-order ones previously observed in Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The double perovskite Sr2CrIrO6 has very important characteristics for spintronic applications. It is a ferrimagnetic material distinguished by its high Curie temperature. This manuscript presents a model representing the double perovskite Sr2CrIrO6 in order to simulate and to predict its magnetic properties. This compound contains only two magnetic atoms, namely: Cr (S = 3/2) and Ir (σ = 2). Our simulations are done using the Monte Carlo method under the Metropolis algorithm. We present the behavior of the magnetization and the susceptibilities as a function of the temperature. Also, we discuss the effect of the physical parameters such as the coupling exchange interactions, the crystal field and the external magnetic field. To complete this study, we have presented the ground state by exposing the different phase diagrams in different planes of the physical parameters. Moreover, we establish the magnetic hysteresis loops of this compound. • We study the magnetic properties of the double perovskite Sr2IrCrO6. • We perform Monte Carlo simulations to investigate the magnetic properties of the double perovskite Sr2IrCrO6. • The effect of the physical parameters is studied and discussed. • The hysteresis loops are also presented for specific values of the physical parameters. [ABSTRACT FROM AUTHOR]

Highlights • Magnetic H - T phase diagram of a Fe/Gd ferrimagnetic superlattice is obtained. • Collinear, twisted and surface twist magnetic states are identified. • Two spectral branches of ferromagnetic resonance are observed. • The observed modes correspond to different types of non-uniform precession in Gd. Abstract Static and dynamic magnetic properties of a ferrimagnetic Fe (35 Å) / Gd (50 Å) 12 superlattice were investigated in a wide 4–300 K temperature range using magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR) techniques. The multilayer structure was sputtered on a transparent glass substrate which made it possible to perform MOKE measurements on both Fe and Gd terminated sides of the superlattice. These experiments allowed us to detect a transition between field-aligned and canted magnetic states on both sides of the film and to distinguish between the bulk and surface twisted phases of the superlattice. As a result, the experimental H - T magnetic phase diagram of the system was obtained. FMR studies at frequencies 7–36 GHz demonstrated a complex evolution of absorption spectra as temperature decreased from room down to 4 K. Two spectral branches were detected in the sample. Theoretical simulations show that the observed spectral branches correspond to different types of inhomogeneous resonance modes in the multilayer with non-uniform magnetization precession inside Gd layers. [ABSTRACT FROM AUTHOR]

Abstract The ferrimagnetic-ferromagnetic-ferrimagnetic quaternary alloy is constructed on the Bethe lattice in the compound form as AB p C q D r and formulated in terms of the exact recursion relations in the standard-random approach. The QA is designed on the BL by placing the A atoms (spin-1) only on the sites of odd shells and randomly placing B (spin-3/2), C (spin-5/2) or D (spin-2) atoms with probabilities, or concentrations, p , q and r , respectively, on the sites of even shells. The phase diagrams are obtained from the thermal analysis of the order-parameters. It is also found that the model yields only one compensation temperature. Highlights • The ferrimagnetic‐ferromagnetic‐ferrimagnetic quaternary alloy (QA) is constructed on the Bethe lattice. • The QA is taken in the compound form as ABpCqDr and formulated in terms of exact recursion relations. • The randomization is applied in the standard‐random approach. • The A, B, C and D atoms are taken as spin‐1, spin‐3/2, spin‐5/2 and spin‐2, respectively. • The phase diagrams are studied from the thermal analysis of the order‐parameters. [ABSTRACT FROM AUTHOR]

The ferrimagnetic mixed spin-1/2 and spin-1 cubic Ising nanowire is studied in the framework of the Monte Carlo simulation. The competition between the bilinear interaction and crystal field of spin-1 atoms as well as the nanowire size effect is highlighted. The corresponding phase diagram is discussed showing compensation points and critical second-order phase transitions. The effect of an external magnetic field and the hysteresis loops behavior are also carried out. Finally, we compare our results with other works in the literature. [ABSTRACT FROM AUTHOR]

We proposed a ferrimagnetic mixed-spin (1, 3/2) Ising model to study the magnetic behaviors of a graphene ladder-type chain structure by means of Monte Carlo simulation. Induced by different physical parameters, the system can display interesting magnetic behaviors such multiple saturation magnetization values, double-peak susceptibility curves, and multi-cycle hysteresis loops. The results illustrate that crystal-field, exchange coupling and external magnetic field show significant impacts on the magnetic properties of the system. • A mixed-spin (1, 3/2) Ising model was proposed to describe a ferrimagnetic graphene ladder-type chain structure. • Magnetization, magnetic susceptibility, and internal energy were studied by Monte Carlo method. • The phase diagrams of the blocking temperature in three-dimensional space was given. • Multi-cycle hysteresis behaviors were discovered caused by various parameters. [ABSTRACT FROM AUTHOR]

Compensation temperature T comp and transition temperature T C have significant applications for the experimental realization of magnetic nanotube structure in the field of thermal magnetic recording. In this work, we use the Monte Carlo simulation to investigate the phase diagrams, magnetizations, susceptibilities, internal energies, specific heats and hysteresis behaviors of a cylindrical ferrimagnetic nanotube with core-shell structure. The effects of the single-ion anisotropies ( D C , D S ) and the exchange couplings ( J int , J S ) on the magnetic and thermodynamic properties of the system are examined. A number of characteristic behaviors are discovered in the thermal variations, depending on different physical parameters. In particular, the triple hysteresis loops behavior has been found for appropriate physical parameters. These findings are qualitatively in good agreement with related experimental and the other theoretical results. [ABSTRACT FROM AUTHOR]

We investigate magnetic quantum phases and the topological quantum phase transition between two distinct valence-bond solid (VBS) phases of a minimal interacting spin-chain model that captures a magnetic behavior of the novel low-dimensional quantum ferrimagnetic material Cu 2 Fe 2 Ge 4 O 13. The studied mixed-spin Heisenberg tetramer chain consists of a 4-period array of spins involving two types of dimers s a − s a ( s a = 1 / 2) and S b − S b ( S b = 5 / 2) under the assumption of unique intra- and inter-dimer coupling constants J 1 and J 2 , respectively. Using the tensor-network formulation of the density-matrix renormalization group method, we have constructed the ground-state phase diagram in the parameter space magnetic field versus the interaction ratio J = J 2 / J 1 , whereby all ground states are in accordance with the Oshikawa–Yamanaka–Affleck theorem for a given period. In addition, we have implemented the recent tangential finite-size scaling method in order to characterize the critical behavior of the topological VBS transition through calculation of the critical point J c and the critical exponent of the correlation length ν. Our results are consistent with the topological quantum phase transition from the SU(2) Wess–Zumino–Witten universality class with the critical exponent of correlation length ν = 2 / 3 by assuming the proper logarithmic correction. • A tetramer ferrimagnetic spin chain with alternate exchange couplings is considered. • The ground-state phase diagram presents magnetization plateaus and spin-liquid phases. • The system presents a topological quantum phase-transition at zero field. • The zero-field transition is between trivial and non-trivial topological phases. • A finite-size analysis unveils a logarithmic correction to the power-law scaling. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the next-nearest neighbors exchange couplings on the magnetic and thermal properties of the ferrimagnetic mixed-spin (2, 5/2) Ising model on a 3D honeycomb lattice have been investigated by the use of Monte Carlo simulation. In particular, the influences of exchange couplings ( J a , J b , J an ) and the single-ion anisotropy( D a ) on the phase diagrams, the total magnetization, the sublattice magnetization, the total susceptibility, the internal energy and the specific heat have been discussed in detail. The results clearly show that the system can express the critical and compensation behavior within the next-nearest neighbors exchange coupling. Great deals of the M curves such as N-, Q-, P- and L-types have been discovered, owing to the competition between the exchange coupling and the temperature. Compared with other theoretical and experimental works, our results have an excellent consistency with theirs. [ABSTRACT FROM AUTHOR]

We investigate the magnetic properties of the mixed spin-1/2 and spin-1 Ising ferrimagnetic system with four-spin interactionJ4and next-nearest neighbor (NNN) couplingJ′. We perform exact ground-state calculations and use the finite cluster approximation, based on a single cluster theory, to derive the state equations for the two-dimensional square lattice. The main attention has been paid to the study of the phase diagram for both the transition and compensation temperatures. We find a number of characteristic behaviors. The model with only NNNs induces one compensation point while the four-spin interaction does not. The investigation of the model with both interactions shows a number of characteristic behaviors. In particular, the presence of the four-spin interaction, according toJ4andJ′, may lead to one, two or possibly a continuum of compensation points. This phenomenon may have important applications in technology such as thermomagnetic writing and erasing at the compensation point. [ABSTRACT FROM PUBLISHER]

Monte Carlo simulation has been used to study magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) Ising nanowire with hexagonal core-shell structure. The ground phase diagrams are obtained for different exchange couplings. The critical values of the exchange couplings have been found, determining whether the compensation points appear in the present system. In particular, the effects of the exchange couplings and the temperature on the magnetization, the internal energy, the specific heat, the compensation points and hysteresis loops are discussed in detail. Under certain physical parameters, multiple cycle hysteresis loops such as triple and quintuple hysteresis loop patterns have been observed in the system. It is found that the exchange coupling and the temperature strongly affect the coercivity and the remanence of the system. Compared our results with other theoretical and experimental studies, a good agreement has been obtained qualitatively. [ABSTRACT FROM AUTHOR]

By using Monte Carlo simulations for classical Heisenberg spins, we study the critical phenomena and ferrimagnetic properties of spherical nanoparticles with core-shell geometry. The particle core is composed of ferromagnetic spins, and it is coated by a ferromagnetic shell. Total size of the particle is fixed but the thickness of the shell is varied in such a way that the shell layer is grown at the expense of the core. Effects of the shell thickness, as well as dynamic magnetic field parameters such as oscillation period and field amplitude on the magnetization profiles, dynamic hysteresis loops and phase diagrams have been investigated for the present system. It has been found that as the shell thickness varies then the easy axis magnetization of the overall system may exhibit Q -, P -, L - and N - type behaviors based on the Neél terminology. We also found that three distinct anomalies originate in the thermal variation of specific heat with increasing field period. Dynamic hysteresis loops corresponding to off-axial magnetization components exhibit unconventional behavior such as double rings with symmetric shapes around the vertical axis over the h ( t ) = 0 line which may originate due to the stochastic resonance behavior of these components. [ABSTRACT FROM AUTHOR]

A hexagonal nanowire consisting of a ferromagnetic spin– 1 2 core and spin– 3 2 outer shell coupled with ferrimagnetic interlayer coupling has been studied by the use of the Monte Carlo simulation based on the heat bath algorithm. Particular emphasis is given to the effects of the size, the crystal field, the shell and the interface coupling constants on the critical and the compensation phenomenon. Some interesting behaviors have been observed which include the first and second order phase transitions. The isolated critical points are also observed. We have also found that the system exhibits the compensation phenomenon for appropriate values of the system parameters. The critical exponent has also been calculated. [ABSTRACT FROM AUTHOR]

The hysteresis properties and phase diagrams of a ternary nanowire, composed of a ferromagnetic (FM) core of spin-1 encircled by a ferrimagnetic (FiM) shell of mixed spin-(1/2, 3/2). Monte Carlo simulation is used to study the effects of the exchange interactions (R s , R 1 , R 2 and R I F) and crystal fields (D c , D s) on the phase diagrams for various thicknesses of core and shell of the system. Our outcomes indicate that the compensation temperature exists for a particular range when D c and D s are present. In addition, a first and a second order phase transitions appear for different values of D c , while a second phase transition appears for various values of D s. Moreover, the hysteresis loops, coercivities and remanences of the system and three sublattices are discussed in detail. Multiple hysteresis loops such as double, triple and quintuple loops were found in the system for a various physical parameters. By comparing our findings to those of previous theoretical and experimental studies, a qualitative agreement can be found. [ABSTRACT FROM AUTHOR]

The phase diagrams and the magnetic properties of a spherical ferrimagnetic nanoparticle, consisting of a ferromagnetic core of atoms A with spin-1/2 ( S A = 1 / 2 ) surrounded by a disordered ferrimagnetic binary alloy shell of two kinds of atoms ( A and B ) with different spins ( S A = 1 / 2 and S B = 3 / 2 ) are studied by using Monte Carlo simulation based on the Metropolis algorithm. Depending on the values of the Hamiltonian parameters, the system presents a number of outstanding phenomena, such as the possibility of one, two or even three compensation point(s). The existence of a compensation temperature is an interesting phenomenon with important technological applications in the field of thermomagnetic recording. [ABSTRACT FROM AUTHOR]

• A multi-walled mixed spin (1/2; 1; 1/2; 1) Ising nanowire with a basic hexagonal shape is built. • For ferrimagnetic and ferromagnetic sates, different magnetic properties are established. • The magnetization types and compensating behaviors are strongly influenced by different Hamiltonian settings. • Unique outcomes are discovered. Using the Effective Field Theory with correlation, we investigate the magnetic properties and the phase diagram of a mixed-spin (½, 1, ½, 1) Ising core-multi shell nanowire structure. Typical temperature dependence of the total magnetization, the core and shell magnetization for several fixed values of exchange couplings were discussed in detail. The phase diagrams of the critical and compensation temperatures were displayed in various Hamiltonian parameter planes. Our established results have been successfully compared with results from several experimental and theoretical studies. The ultimate objective is to stimulate research into the design and development of innovative nanomaterials for targeted applications. [ABSTRACT FROM AUTHOR]

The phase diagrams and magnetizations of Ising nanowires with simple core–shell structure are investigated by the use of the effective field theory with correlations. A lot of characteristic behaviors observed in ferromagnetic and ferrimagnetic materials as well as novel phenomena have been obtained, although one section of the system is consisted of one spin-1/2 surface shell atom and one spin-1/2 core atom and they are coupled with a positive or a negative shell–core exchange interaction. [ABSTRACT FROM AUTHOR]

The magnetic properties of Ising nanoisland with a ferrimagnetic spin-1 and 3/2 configuration are studied by Monte Carlo simulation. The ground state phase diagrams of mixed spins are obtained. The critical temperature is obtained for different values of exchange interactions and for different crystal fields. The magnetic hysteresis cycle is obtained with different values of temperature, exchange interactions, and crystal field values. The applications of the Monte Carlo to the magnetic properties are extremely restricted for nanoislands, when the value of an interlayer coupling takes a large value, in contrast to a number of bulk studies. [ABSTRACT FROM AUTHOR]

Within the effective-field theory (EFT), the compensation behaviors in molecular-based ferrimagnet A F e Ι Ι F e Ι Ι Ι ( C 2 O 4 ) 3 which is described by a mixed spin-2 ( F e Ι Ι ) and spin-5/2 ( F e Ι Ι Ι ) ferrimagnetic Ising model on a honeycomb lattice are studied. The Glauber-type stochastic dynamic is used to describe the time evolution of the system under an oscillating magnetic field. A magnetic field dependence of the compensation temperature and a temperature dependence of compensating magnetic field are calculated and both curves agree qualitatively with experimental data. In particular, a two-compensation-points phenomenon which has been reported in the experimental work is also observed in this compound. Dynamic phase boundaries containing the compensation points are calculated. The dynamic tricritical point and critical end point exist on the phase transition lines. Comparing with previous theoretical results obtained by the mean-field theory (MFT), the effective-field theory results show a reasonable improvement over the MFT results. [ABSTRACT FROM AUTHOR]