Magnetic Hysteresis Cycles Research Articles

Magnetic properties of Kekulene structure: A Monte Carlo study

The magnetic properties of magnetic Kekulene structure with mixed spins-5/2 and 2 Ising model have been studied using Monte Carlo simulations. The ground state phase diagrams of system Ising model and the thermal magnetization have been obtained. The transition temperature has been determined. The effect of reduced crystal field and exchange interactions on the magnetic Kekulene structure are studied. Finally, the magnetic hysteresis cycles of the mixed spins-5/2 and 2 Ising model on a magnetic Kekulene structure have been obtained for a several values of crystal field, exchange interactions and temperatures values. The superparamagnetism behavior is observed in Kekulene structure.

Structural and magnetic properties of cobalt clusters Con (n = 2–6)

ABSTRACTThe geometrical structures and magnetic properties of (n = 2–6) magnetic clusters have been systematically investigated using Monte Carlo simulations. The transitions temperatures are deduced from the thermal magnetisation and magnetic susceptibility of for different size. The effect of crystal fields and exchange interactions on the magnetisation has been investigated. Magnetic hysteresis cycles with different clusters, temperatures and exchange interactions are obtained. Superparamagnetism in cobalt clusters has been observed.

Surface effects on the magnetocaloric properties of perovskites ferromagnetic thin films: A Monte Carlo study

We have used the Monte Carlo simulations to study the surface effects on the magnetocaloric properties of perovskites ferromagnetic thin films. We have determined the magnetization, the transition temperatures, magnetic entropy change, the relative cooling power (RCP), and the magnetic hysteresis cycle temperature as functions of the film thickness, and surface exchange coupling. The reduced critical temperature tC of the perovskites ferromagnetic thin films is studied as a function of film thickness L and the exchange interactions in the bulk JB, in the surface JS and between surface. We have shown that maximal entropy change in thin film systems can be observed at temperatures well below the magnetic phase transition temperature. The maximal entropy change increases with increasing the external magnetic field. RCP increases with increasing the external magnetic field and it is dependent of thickness film. The RCP decreases with increasing the value of surface exchange coupling. The magnetic coercive field decreases with increasing the temperatures values when the surface exchange coupling is inferior to bulk exchange coupling. The magnetic coercive field hC of the perovskites ferromagnetic thin films is studied as a function of reduced surface exchange coupling.

Synthesis, crystal structure, magnetic properties and DFT calculations of a mononuclear copper(II) complex: Relevance of halogen bonding for magnetic interaction

The synthesis, crystal structure, magnetic properties and DFT calculations of a new mononuclear copper(II) complex containing a pyrazole-based ligand are reported. In the crystal structure of the [CuCl2L2] complex (L = Ethyl 5-amino-1-(4-methoxyphenyl)-1H-pyrazole-4-carboxylate), a network of hydrogen bonds connects the molecular units in the crystal packing. The magnetic studies revealed predominant antiferromagnetic interactions among molecular units. Since there are multiple intermolecular contacts that can act as pathway for magnetic interactions, DFT calculations revealed the fundamental role of N–H⋯Cl short intermolecular contacts in magnetic behavior. Supported by DFT calculation, the magnetic data above 7.0 K was modeled as a regular Heisenberg chain (H=-2J∑i=1n-1S→Ai·S→Ai+1) resulting in a weak magnetic coupling constant (J) of −2.6 cm−1. Below this temperature, an unusual magnetic behavior for mononuclear copper(II) complexes was observed: divergence between zero-field cooled (ZFC) and field cooled (FC) magnetic susceptibilities and magnetic hysteresis cycles at low temperatures attributed to spin canting along the chain.

Study of Magnetocaloric Effect on Strontium Ferrite SrFe12O19 Ceramic

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.

Preparation of magnetic glass-ceramics by crystallization of ternary eutectic Li2O-MgO-SiO2 system reformed with some di-and trivalent oxides

This work sheds light on influence of replacing MgO by SrO, MnO or Fe2O3 on the crystallization and magnetic properties of glass-ceramics based on the ternary Li2O-MgO-SiO2 eutectic (935 ± 10 °C) system. Moreover, the effect of adding Al2O3 was also studied. All the glass samples were prepared by the conventional melting technique. Magnetic hysteresis cycles were analyzed using a vibrating sample magnetometer with applied magnetic field up to 20 kOe at room temperature. The bulk density and Vicker microhardness were also evaluated. The crystalline phases formed are lithium meta- and di-silicate, MgSiO3, SrSiO3, Sr-akermanite (Sr2MgSi2O7), β-MnSiO3 and four crystalline phases of pyroxene type like Kanoite-MgMnSi2O6, β-spodumene and Li-aegirine (LiFeSi2O6) with its solid solution (Li,Mg)FeSi2O6. Spinel-LiFe5O8 magnetic phase was also detected. The density values of the examined glass-ceramics are between 2.48 and 2.91 g/cm3. A dense fine microstructure provides superior hardness glass-ceramics up to 6523 MPa is also obtained. The obtained magnetization data is mainly related to the nature of crystalline phases formed and the resulting microstructure. The results reveal an improvement in the magnetization and mechanical properties which render the prepared glass-ceramics useful for hyperthermia treatment of cancer-like bone tumors and for electronic devices as magnetic disk substrates.

Monte Carlo simulations of magnetic properties of Kekulene structure bilayers separate by a nonmagnetic with RKKY interactions

The magnetic properties of magnetic bilayers of Kekulene structure separate by a nonmagnetic layer with Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interactions with Ising spin model have been studied using Monte Carlo simulations. The RKKY interaction between the bilayers of Kekulene is considered for different distances. The transition temperature has been deduced from the magnetizations and magnetic susceptibilities partial for a fixed value of nonmagnetic layer. The reduced transition temperatures are also deduced from the total magnetization and total magnetic susceptibilities with different values of L. The magnetic hysteresis cycles of systems have been determined.

Magnetic Properties of the Triangular Lattice with Different Clusters: A Monte Carlo Study

The magnetic properties of the triangular lattice with different clusters have been studied using the Monte Carlo simulations. The reduced transitions temperatures are deduced for different size of clusters L and for different exchange interactions. The variation of magnetization with the crystal field is given for different size of clusters and exchange interactions. Finally, the magnetic hysteresis cycles are found for different values of size of clusters and reduced temperatures. We found that the magnetic coercive fields increases with increasing the size of clusters and decreases with increasing the reduced temperatures.

Magnetic properties of magnetic bilayer Kekulene structure: A Monte Carlo study

In the present work, we have studied the magnetic properties of magnetic bilayer Kekulene structure with mixed spin-5/2 and spin-2 Ising model using Monte Carlo study. The magnetic phase diagrams of mixed spins Ising model have been given. The thermal total, partial magnetization and magnetic susceptibilities of the mixed spin-5/2 and spin-2 Ising model on a magnetic bilayer Kekulene structure are obtained. The transition temperature has been deduced. The effect of crystal field and exchange interactions on the this bilayers has been studied. The partial and total magnetic hysteresis cycles of the mixed spin-5/2 and spin-2 Ising model on a magnetic bilayer Kekulene structure have been given. The superparamagnetism behavior is observed in magnetic bilayer Kekulene structure. The magnetic coercive field decreases with increasing the exchange interactions between σ-σ and temperatures values and increases with increasing the absolute value of exchange interactions between σ-S. The multiple hysteresis behavior appears.

Size and diluted magnetic properties of diamond shaped graphene quantum dots: Monte Carlo study

The magnetic properties of diamond shaped graphene quantum dots have been investigated by varying their sizes with the Monte Carlo simulation. The magnetizations and magnetic susceptibilities have been studied with dilutions x (magnetic atom), several sizes L (carbon atom) and exchange interaction J between the magnetic atoms. The all magnetic susceptibilities have been situated at the transitions temperatures of each parameters. The obtained values increase when increases the values of x, L and J. The effect of exchanges interactions and crystal field on the magnetization has been discussed. The magnetic hysteresis cycles for several dilutions x, sizes L, exchange interactions J and temperatures T. The magnetic coercive increases with increasing the exchange interactions and decreases when the temperatures values increasing.

An Ising Spin-2 Model on Generalized Recursive Lattice: a Monte Carlo Study

The magnetic properties of Ising spin-2 model on recursive p-polygonal structures are studied using Monte Carlo simulations. The thermal magnetization and magnetic susceptibility of recursive 1-, 2-, 3-, and 4-polygonal structures have been terminated. The variation of magnetization and magnetic susceptibility of recursive 2-polygonal structures for several external magnetic field and the variation of magnetization and magnetic susceptibility versus the crystal field and temperatures of recursive 1-, 2-, 3-, and 4-polygonal structures are given. Finally, the magnetic hysteresis cycle of recursive 1-, 2-, 3-, and 4-polygonal structures are obtained and for different temperatures with 2-polygonal structures. It is shown that the reduced transition temperature increases with increasing the p-polygonal structures and decreases with increasing the absolute value of crystal field. The magnetic coercive field increases with increasing the p-polygonal structures and decreases with increasing the temperature values. The superparamagnetism behavior is observed in our system at around reduced transition temperature.

Electronic, magnetic properties and phase diagrams of system with Fe4N compound: An ab initio calculations and Monte Carlo study

Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate the electronic and magnetic properties of the Fe4N compound. Polarized spin and spin-orbit coupling are included in calculations within the framework of the ferromagnetic state between Fe(I) and Fe(II) in Fe4N compound. We have used the obtained data from abinitio calculations as an input in Monte Carlo simulation to calculate the magnetic properties of this compounds such as the ground state phase diagrams, total and partial magnetization of Fe(I) and Fe(II) as well as the transition temperatures are computed. The variation of magnetization with the crystal field are also studied. The magnetic hysteresis cycle of the same Fe4N compound are determined for different values of temperatures and crystal field values. The two-step hysteresis loop are evidenced, which is typical for Fe4N structure. The ferromagnetic and superparamagnetic phase is observed as well.

Magnetocaloric effect and magnetic properties in SmFe1-xMnxO3 perovskite: Monte Carlo simulations

We have used Monte Carlo simulation to study the magnetocaloric effect on SmFe1-xMnxO3 perovskite. The temperature-dependent magnetization shows that the Néel temperature of the weak-ferromagnetic SmFeO3 decreases as Fe ions are substituted by Mn ions. A paramagnetic-to-weak-antiferromagnetic transition with decreasing the temperature is observed and the corresponding Néel temperature essentially decreases as the Mn content increases. The magnetocaloric effect shows two peaks related to magnetic behavior changes, at paramagnetic-like behavior TK(K) and at Néel temperature TN(K) of SmFe1-xMnxO3. The second phase transition is established. The magnetic entropy change is given for a several magnetic fields. We have also determined the relative cooling power for dilution x = 0.5 and for a several external magnetic fields. Finally, the magnetic hysteresis cycles have been obtained with different dilutions x and temperatures values.

Magnetic properties of cluster dendrimers of core/shell with mixed spins σ = 3/2 and S = 2: A Monte Carlo study

Monte Carlo simulation is used to study the magnetic properties of cluster dendrimers (CD) of core/shell (CDCS). The ground state phase diagrams of the CD of core/shell with mixed spins σ = {±3/2; ±1/2} and S = {±2; ±1; 0} has been determined. The Néel temperature tN is obtained for two configurations (z = 2 and z = 3) and for different size of system. There is magnetic compensation at non-zero temperature for z = 2. Effect of exchange interactions between the mixed spins, crystal field and size of system(L) on total magnetization has been given. Magnetic hysteresis cycle is given for different size of system, temperatures and exchange interactions.

Magnetic properties and Binder cumulants of a mixed spin-2 and spin-5/2 Ising diamond chain

The mixed spin-2 and spin-5/2 Ising diamond chain is studied using Monte Carlo simulation. The thermal variation of magnetization and magnetic susceptibilities are obtained in diamond chain. The values of transition temperatures of a mixed spin-2 and spin-5/2 Ising diamond chain have been obtained for different sizes of system N, for different crystal field and for different exchange interactions. The Binder cumulant of magnetization [Formula: see text] is investigated. The magnetization with the crystal field and the exchange interaction has been established. The magnetic hysteresis cycle is determined for different values of the crystal field, exchange interactions and temperatures. The system presents the superparamagnetic behavior for a fixed crystal field and temperature value.

Magnetic properties and magnetocaloric effect in double Sr2FeMoO6 perovskites

The magnetic properties and magnetocaloric effect in Sr2FeMoO6 compound have been studied using the Monte Carlo simulation. Thermal magnetization and dM/dT of Sr2FeMoO6 are given. The Curie temperatures TC(K) have been obtained. The temperature dependence of the magnetic entropy for a several magnetic field have been also obtained. The field dependence of relative cooling power and magnetic hysteresis cycle of Sr2FeMoO6 have been determined for a several magnetic field and temperatures. The Sr2FeMoO6 might be a promising base for developing the new kinds of magnetic refrigerant as working materials in magnetic refrigeration technology.

Magnetic properties of the Ising system on alternate layers of a hexagonal lattice

The magnetic properties of the mixed spin-1 and spin-5/2 Ising ferrimagnetic model on a hexagonal lattice have been studied using the Monte Carlo simulations. The hexagonal lattice study is formed by alternate layers of spins σ=1 and S=5∕2. The thermal variations of the magnetizations are given. The magnetic hysteresis cycles are established for different values of exchange interactions, crystal-field and temperatures. The magnetic coercive field is deduced.

Ground state and magnetic phase transitions of the spin Lieb nanolattice: Monte Carlo simulations

We study the ground state and magnetic properties of the spin Lieb nanolattice with three lattice sites with spins (S=2,σ=1∕2,q=3∕2) using Monte Carlo simulations. The ground state phase diagrams of the Lieb nanolattice have been studied. The phase diagrams show some key features: coexistence between regions, points where six, eight and ten states can coexist. The total and partial magnetization of each sublattice is given and the corresponding magnetic susceptibility is also found. The variation of total magnetization with the exchange interaction RSq and Rσq of the Lieb nanolattice with three lattice sites with spins (S,σ,q) has been studied. Moreover, the total magnetization versus the fields Δ∕JSσ of the Lieb nanolattice with three lattice sites with spins (S,σ,q) are established for several values of Rσq and Rsq. Magnetic hysteresis cycles of the Lieb nanolattice with three lattice sites with spins (S,σ,q) are found for several values of Rsq and temperature. We show that the superparamagnetism behaviour appears for a weak coupling value between S and q thus around the transition temperature.

Dependence of the Magnetic Transition Temperatures T N 1 and T N 2 and Magnetization Plateau of the 2D Checkerboard Lattice Structure with the Superblock (N,N)

Magnetic properties of the 2D checkerboard lattice structure with the superblock (N,N) were studied using Monte Carlo simulation based on the Ising model. Thermal magnetization and magnetic susceptibility of 2D checkerboard lattice with several superblocks are given. Two magnetic anomalies at collinear-to-spiral transition temperature t C1 and transition temperature t C2have been determined. We discuss the effect of exchange interactions and superblocks on 2D checkerboard lattice. Magnetic hysteresis cycle of 2D checkerboard lattice for several superblocks have been shown. Superparamagnetic behaviour has been observed. Magnetization plateau, visible as anomalies in magnetic hysteresis, is one of the hallmarks of frustrated magnetism.

Surface behavior of magnetic phase transitions: A Monte Carlo study

In this manuscript, we have studied the magnetic properties of superlattice with simple cubic lattice formed by mixed spin-5/2 in surface and spin-2 in bulk using the Monte Carlo simulations. The ground state of this system is given. The critical temperature has been deduced and discussed. The thermal behaviors of the magnetizations as well as the effect of the different exchange interactions and the crystal field effect, have also been studied. The magnetic hysteresis cycles of such system has been discussed for different values of the exchange interactions between superlattice, for different values of the crystal field and for different temperature values. The effects of the crystal fields, temperatures and the increase in the number of interactions induce greater complexity in the phase diagrams, causing various multiphase points and multiples of hysteresis cycles and allow exploring regions where important magnetic behaviors could arise.