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[en] The magnetic properties of ferrimagnetic mixed-spin Ising model in the checkerboard lattice are studied using Monte Carlo simulations. The variation of total magnetization and magnetic susceptibility with the crystal field has been established. A transition from an order to a disordered phase has been obtained in some critical value of the physical variables. The reduced transition temperature is obtained for different exchange interactions. The magnetic hysteresis cycles have been established. The multiples hysteresis cycle in checkerboard lattice are obtained. The multiples hysteresis cycle have been established. The ferrimagnetic mixed-spin Ising model in checkerboard lattice is very interesting from the experimental point of view. The mixed spins system have many technological applications such as in domain opto-electronics, memory, nanomedicine and nano-biological systems. The obtained results show that that crystal field induce long-range spin–spin correlations even bellow the reduced transition temperature
[en] Highlights: • Magnetic properties of the 3d-4d double perovskite Sr2CrMoO6 have been studied. • The system is stabilized at ground state by the ferromagnetic phase of core spins. • Effective spins Hamiltonian and the exchange coupling effects have been investigated. - Abstract: In this work, we use the exact diagonalization and Monte Carlo calculations to study magnetic behaviors of the 3d-4d double perovskite Sr2CrMoO6. The model is described by a quantum Hamiltonian induced by the hybridization mechanism in Sr2CrMoO6 via the double exchange, considering the transition metal Mo5+ (σ = 1/2, 4d1) cation totally non-magnetic and classical core spins S = 3/2 located at sites of Cr3+ (S = 3/2, 3d3) cations. We have defined a Hamiltonian matrix and determined eigen-energies which are functions of core spins interactions. At ground state, we have found that the ferromagnetic phase of core spins stabilizes the system for the electronic density n = 0.25. To study magnetic properties at finite temperature, we have defined an effective magnetic Hamiltonian for spins, approving the Monte Carlo simulations for systems of high sizes. Thus, the exchange coupling effect, the magnetization and the magnetic susceptibility are investigated for different sizes, and the critical temperature is determined.
[en] We use standard Monte Carlo simulations based on the Metropolis algorithm and mean-field calculations to investigate the magnetic properties of an Ising bilayer film consisting of two superposed ferromagnetic squared lattices A and B whose magnetic atoms have spin 7/2 and 5/2 respectively. Crystal-field and external magnetic field effects on the spins are considered in the model. The magnetic order parameters and response functions are calculated as functions of the temperature for selected values of the model parameters and this enables one to devise thermal phase diagrams by both methods. Our calculations only reveal second-order phase boundaries. Under appropriate conditions, compensation point phenomena are detected in the calculations below the critical temperatures. When the system is exposed to the external magnetic constraint, attracting hysteresis phenomena are sometimes generated. The temperature dependence of the coercitive field for various values of the crystal-field is singled out.
[en] Magnetocaloric effect on SrFe12O19 ceramic have been studied using Monte Carlo simulation. The thermal magnetization, dM/dT, magnetic entropy, and the specific heat of SrFe12O19 ceramic are obtained for several magnetic fields. The temperatures dependence of the magnetic entropy and of the adiabatic temperature for a several magnetic field have been obtained. The field dependence of relative cooling power (RCP) of SrFe12O19 ceramic has been determined for a several magnetic fields. The magnetic hysteresis cycle of SrFe12O19 ceramic has been obtained for a several temperatures. The obtained values are close to the experimental values. The transition paramagnetic to ferromagnetic is found at the Curie temperature. The second phase transition is also obtained around the Curie temperature.
[en] In this paper, we used the ab-initio calculations, based on the Korringa-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA), to simulate the magnetic properties of ZnO, doped and co-doped with manganese and carbon, respectively. For this purpose, we have used two different approximations: the Local Density Approximation (LDA) and the Local Density Approximation-Self-Interaction Correction (LDA-SIC). Numerical results are presented for the compound Zn1 − 0.06Mn0.06O1−xCx when doping and co-doping is performed with Mn and C as doping elements. Total and partial DOSs are given for different concentrations using the two approximations, LDA and LDA-SIC. It is found that for 6% with doping by Mn the system becomes magnetic. The co-doping with carbon changes the behavior of the system : it becomes also magnetic for 4, 6 and 10% concentrations within both, LDA and LDA-SIC approximations. Furthermore, we have discussed the type of mechanism of exchange interaction and found that the double exchange is responsible for the appearing magnetism in the system, within the LDA and p-d interaction for LDA-SIC approximation. For 10% of carbon, we have found that the critical temperature approaches 280 K in the LDA approximation solely; and is about 305 K in the LDA-SIC approximation.
[en] The ferrimagnetic systems have been extensively investigated because of their fascinating properties. In this paper, the mixed spin-7/2 and spin-3 Ising system with periodic boundary conditions on a square lattice has been studied using the Monte Carlo simulation within the Metropolis algorithm; the Hamiltonian of the system includes the interaction between the first nearest neighbors and the crystal fields Δ7/2 and Δ3 generated by the spin-7/2 and spin-3, respectively. The ground-state phase diagram of the system has been established. On the other hand, the impact of the single-ion anisotropies on the compensation temperature has been shown. Several topologies of the total magnetization have been found for this system.
[en] Highlights: • We employ Monte Carlo simulation technique to Ising model spin in bilayer square lattice. • We study effect of external magnetic field, crystal filed and exchange interactions in AFM/FM bliayer. • The magnetic coercive field is deduced. The magnetic behavior of the mixed spin-1 and spin-3/2 Ising system on a bilayer square lattice is studied using the Monte Carlo simulations for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions in the presence and absence of external magnetic, crystal field and for different values of exchange interactions. The thermal variations of the magnetizations are given. The magnetic hysteresis cycles are established. The magnetic coercive field and the remanent magnetization are deduced. The coercive magnetic field, remanent magnetization and the transition temperature were not affect by the size effect.
[en] In this paper, the magnetism of ZnO with wurtzite-type structure, when doped with Fe then co-doped with (Fe,V) was investigated by density functional theory. Furthermore, the difference between the ferromagnetic and the disordered local moment in term of magnetic energy indicated the stabilization of the magnetic phase in diluted magnetic semiconductors. It was revealed that the semi-metallic behaviour in Zn0.95Fe0.05O composition was transferred to a half-metallic behaviour with co-doping with V. Hence, the Fermi level was crossed by the majority-spin valence states, meanwhile, a gap occured in the Fermi level of the minority-spin states. A large replacement splitting was detected between V 3d states of the majority-spins and the minority-spins. The estimated Curie temperature was found to increase with V content. X-ay diffraction Rietveld analysis revealed that the co-doping of ZnO with Fe and V maintains the wurtzite crystal structure and that the crystallite size increased with doping concentration, i.e. 15–52 nm. Hysteresis loops indicated the appearance of room temperature ferromagnetism, where the magnetic properties were found to be very sensitive to the nature of the doping element (Fe and Fe-V) as well as its concentration. Both ab initio calculations and experimental results were found in good agreement. The observed changes in the magnetic parameters were attributed to a combination of various parameters, such as the substitution by the magnetic Fe and the non-magnetic V atoms, formation of small crystals in the nanoscale regime, the increase of crystallite size and grain boundaries. (paper)
[en] The magnetic properties of antiferromagnetic CoO compound have been studied using Monte Carlo simulations within the Ising model framework. The thermal magnetizations and magnetic susceptibilities are computed for a fixed size. In addition, the Néel temperature is deduced. The magnetization versus the reduced exchange interactions and crystal field are studied for a fixed system size, N = 10 nm particles. The magnetic hysteresis cycle versus temperature is also established. (author)
[en] Highlights: • The ground-state phases have been determined. • The magnetic and electronic properties of mixed spins based on double Perovskite Oxide Structure have been investigated. • The coupling interaction between different magnetic atoms has been calculated. • The values of the critical exponents are close to the 3D Ising model ones. The magnetic and electronic properties of the double perovskite Lu2MnCoO6 are studied by combining the ab-initio calculations and Monte Carlo simulation (MCs) based on the Ising model. This compound is constituted of two magnetic cubic sublattices: one occupied by Mn4+ with spin (s = 3/2) and other occupied by Co2+ with spin (σ = 3/2). By using ab-initio calculations we compute the exchange coupling between Mn-Co sublattices. We also investigate the phase transitions and the magnetic stability of this compound. The Curie temperature is determined as well as the critical exponents. We show that the Lu2MnCoO6 compound belongs to the 3D-Ising universality class.