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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]

• 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]

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]

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]

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]

• 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 mixed spin Ising model is generally used as a modeling tool to study ferrimagnetism. • Monte Carlo simulation to study the critical and the compensation behaviors of a cubic lattice considering a mixed spin- 3/2 and spin-1 Ising ferrimagnetic model. • The presence of crystal and external magnetic fields is not sufficient to generate the compensation phenomenon in a mixed spins. In this study, we perform Monte Carlo simulations to study the magnetic properties of a mixed Ising model on a cubic lattice where spins S i A = 1 and σ J B = 3/2 are located in sublattice A and B, respectively. The proposed Hamiltonian includes coupling to nearest-neighbors interactions, next-nearest-neighbors interactions, crystal fields D S and D σ and external magnetic field h. We perform exact ground-state calculations for our model. The obtained results show the behavior of the critical temperature with the presence of the compensation temperatures under a certain range of parameters. Particularly, we found that the existence of compensation temperatures depends on the strength of the coupling to the next nearest neighbors between the S i A spins and between the σ J B spins, and it appears in a certain range of values of the external magnetic and crystal field of different spins. [ABSTRACT FROM AUTHOR]

The ability to combine multiple spintronic properties in the Zn x Fe 3- x O 4 system with different variants of its chemical composition offers a new and tantalizing route towards homodevices. This is mainly due to the advantage of varying the Zn component of Zn x Fe 3- x O 4 , which leads to the possibility of preserving spinel symmetry (within 5% lattice mismatch) while changing the material properties from a ferrimagnetic half-metal (x = 0) to an insulating paramagnet (x = 1). Here we demonstrate that Zn x Fe 3- x O 4 thin films, grown from a ZnFe 2 O 4 single phase target, laser-ablated under a reduced atmosphere, exhibits a reduction of Zn content, a large 4πM S (6.5 kG), very low resistivity (25 mΩ cm) and a Verwey transition, all of which can be engineered by an appropriate choice of growth temperature. All these spectacular properties are confirmed by ab initio calculations and can be attributed to the inverse structure of [Zn x +2Fe 1−x +3] A [Fe 1+y +3Fe 1−y +2] B O 4-δ , where the reduced Fe+2 ions along with Fe+3 occupy the octahedral sites while the Zn+2 and inverted Fe+3 sit in the tetrahedral sites. Phase formation in laser ablated Zn x Fe 3- x O 4 thin films are different compared to the bulk thermal equilibrium, and shows that there is a competition between the reduction of Zn and the formation of O vacancies at various growth temperature zones. • Stabilization of ferrimagnetic phase in Zn x Fe 3- x O 4-δ thin films which otherwise difficult. • Observation of all in one spintronic properties (high M, low ρ and half metallicity). • Construction of growth phase diagram of Zn x Fe 3- x O 4-δ and Fe 3 O 4-δ thin films. • DFT calculation of inverted spinel Zn x Fe 3- x O 4-δ for its elusive electro-magnetic properties. [ABSTRACT FROM AUTHOR]

Monte Carlo simulation has been employed to investigate the magnetic properties and phase diagrams of ferrimagnetic mixed-spin (1 / 2 , 1) triangular Ising nanotube with core–shell structure. In particular, the effect of the exchange couplings and the temperature on the magnetic and thermodynamic properties, hysteresis loops, and the compensation temperature have been discussed in detail. Moreover, the effects of the single-ion anisotropy and external magnetic field have been examined. The threshold values of the exchange couplings and single-ion anisotropy have been found, determining whether the system exhibits a compensation temperature. We have found that the appearance of the compensation temperature is strongly linked with the system parameters. Moreover, we have obtained the double and triple hysteresis loops for certain physical parameters in the magnetic system. [ABSTRACT FROM AUTHOR]