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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]

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]

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]

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 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 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]

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]

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]

We have used Monte Carlo simulations based on the Metropolis algorithm to study the magnetic properties of an Ising nanowire with spin-7/2 core and spin-5/2 shell atoms in the presence of lattice anisotropy and external magnetic field. Only antiferromagnetic interfacial interactions are considered. Thermal variations of the order parameters, phase diagrams, and hysteresis behaviors of the model are calculated. The transitions encountered are of different types: first-order, second-order, compensation, and blocking transitions. It has been found that the magnetic properties of the model, in particular the critical behavior, the compensation, and the hysteresis phenomenon, exhibited are strongly affected by the competition between values of system parameters during the simulations. [ABSTRACT FROM AUTHOR]