Results 1 - 10 of 32
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[en] We investigate the magnetic properties of Cayley trees of large molecules with dendrimer structure using Monte Carlo simulations. The thermal magnetization and magnetic susceptibility of a dendrimer structure are given with different coordination numbers, Z=3, 4, 5 and different generations g=3 and 2. The variation of magnetizations with the exchange interactions and crystal fields have been given of this system. The magnetic hysteresis cycles have been established. - Highlights: • The dendrimer structure is investigated using Monte Carlo simulations. • The transition temperatures are obtained for different coordination numbers and generations. • The magnetic hysteresis cycle has been established. • The dendrimer structure exhibit the superparamagnetic behavior.
[en] In this work, the lattice structure of bilayer graphene armchair nanoribbons atoms within the same layer are studied by Monte Carlo simulations. The ground state phase diagrams of mixed spin-3 and spin-7/2 Ising model on a of bilayer graphene armchair nanoribbons are studied using the Monte Carlo simulations. The reduced transition temperatures with the exchange interactions have been given. The total magnetization and magnetic susceptibility with the crystal field have been established for different plane exchange interactions. Finally, we have given the magnetic hysteresis cycle for different plane exchange interactions, different temperatures, and different crystal field in bilayer graphene armchair nanoribbons. The bilayer graphene armchair nanoribbons exhibit the superparamagnetic behavior at the reduced transition temperature and for a fixed of crystal field. - Highlights: • Bilayer graphene armchair nanoribbons is studied by Monte Carlo simulations. • Ground state phase diagrams graphene armchair nanoribbons are studied. • Transition temperature with the exchange interactions have been given. • Magnetic hysteresis cycle of bilayer graphene armchair nanoribbons is given. • Bilayer graphene armchair nanoribbons exhibit the superparamagnetic behavior.
[en] The magnetic properties of mixed spins-5/2 and -2 Ising model on the two alternative layers on a honeycomb lattice are investigated and are discussed using the Monte Carlo simulations. The different ground-state phase diagrams are found. The eight magnetic stable phases are obtained for a fixed magnetic parameters. The critical temperatures are deduced for different layers. The system exhibits the second order and first order phases transitions. The plateau obtained between the high temperature phase and low-temperature phase at critical temperature can be explain by first-order transition. The second order transitions also show continuity in order magnetization at the reduced critical temperatures. The variation of magnetizations with exchange interactions and crystal field in each layer has been given. Magnetic hysteresis cycle has been obtained for different layers, temperatures and crystal fields. (author)
[en] The Monte Carlo simulation is used to investigate the magnetic properties of ferromagnetic superlattices through the Ising model. The reduced critical temperatures of the ferromagnetic superlattices are studied each as a function of layer thickness for different values of exchange interaction. The exchange interaction in each layer within the interface and the crystal field in the unit cell are studied. The magnetic coercive fields and magnetization remnants are obtained for different values of exchange interaction, different values of temperature and crystal field with fixed values of physical parameters. (paper)
[en] In this research uranium concentration was determined in different kind of water (Samples include surface, underground waters,, rain water ,running water, and drinking water in Baghdad ,babil, basra, karbla,najaf, wasit by fluorimetry with high accuracy and the result compared with gamma spectroscopy.In general, the methods of analysis used in this study are applicable for a precise determination of uranium. It can be concluded that, fluorimetry analysis is preferred for assay of uranium ore due to the required small sample weight, the low time of sample preparation and cost of analysis.
[en] Magnetic properties and magnetocaloric effect of the praseodymium–silicon (PrSi)-like compound are studied using Monte Carlo simulation. Thermal magnetization, dM/dT, normalized magnetic entropy and the normalized specific heat of PrSi are given. The temperature dependence of the normalized magnetic entropy and the normalized adiabatic temperature change are obtained. The Curie temperature of PrSi is obtained. The field dependence of normalized relative cooling power of PrSi has been determined. The magnetic hysteresis cycle of PrSi is obtained. Large magnetic entropy change, ΔSm, the relative cooling power and characteristics of giant magnetocaloric effect are achieved near the reduced Curie temperature. (author)
[en] The magnetic properties of a Husimi lattice with antiferromagnetic spins-|S| = 1/2, 1, 3/2, and 2 Ising model with three sites in the elementary polygon (p = 3) and the coordination number z = 4 have been investigated using a Monte Carlo study. The reduced critical temperature is deduced for different values of magnetic external field, for a fixed value of crystal field and spin moments. The magnetization versus the crystal field is determined for different values of temperatures and for different values of external magnetic field and spin moments. The hysteresis curves of magnetization with the magnetic field have been established for different values of reduced temperatures, reduced crystal field, and spin moments.
[en] 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.
[en] The magnetic effect and the magnetocaloric effect in La2NiMnO6(LNMO) double perovskite are studied using the Monte Carlo simulations. The magnetizations, specific heat values, and magnetic entropies are obtained for different exchange interactions and external magnetic fields. The adiabatic temperature is obtained. The transition temperature is deduced. The relative cooling power is established with a fixed value of exchange interaction. According to the master curve behaviors for the temperature dependence of predicted for different maximum fields, in this work it is confirmed that the paramagnetic–ferromagnetic phase transition observed for our sample is of a second order. The near room-temperature interaction and the superexchange interaction between Ni and Mn are shown to be due to the ferromagnetism of LNMO. (paper)
[en] Highlights: • Magnetic properties of bilayer Kekulene with mixed spins Ising model have been studied. • Magnetic phase diagrams of mixed spins Ising model have been given. • Transition temperature of magnetic bilayer Kekulene has been deduced. • Superparamagnetism behaviour is observed in magnetic bilayer Kekulene structure. • Multiple hysteresis behavior appears in bilayer Kekulene with mixed spins Ising model. - Abstract: 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.