Based on Monte Carlo method, the oscillatory behaviour of the average magnetic moment as a function of the cluster sizes and the temperature dependences of magnetic moment with different sizes have been studied. It is...Based on Monte Carlo method, the oscillatory behaviour of the average magnetic moment as a function of the cluster sizes and the temperature dependences of magnetic moment with different sizes have been studied. It is found that the oscillations superimposed on the decreasing moment are associated with not only the geometrical structure effects but also the thermal fluctuation. The hystereses and thermal coercivities for free clusters with zero and finite uniaxial anisotropies have been calculated. The simulated thermal dependence of the coercivity is consistent with the experimental result, but does not fit the T^α law in the whole temperature range. It is evident that an easy magnetization direction and an anisotropy resulting from the spin configurations exist in the free clusters with the pure exchange interaction, which is also proved by the natural angle and energy distribution of clusters. A systematic theoretical analysis is also made to establish the relationship between natural angle and coercivity.展开更多
Using the Monte Carlo method,the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters ...Using the Monte Carlo method,the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters such as crystal field,exchange coupling,external magnetic field,and temperature.The variations of magnetization,magnetic susceptibility,specific heat,and internal energy with the change of temperature are discussed.In addition,we also plot the phase diagrams including transition temperature and compensation temperature.Finally,multiple hysteresis loops under certain parameters are given.展开更多
The intrinsic ferromagnetism of CoBr2 bulk was investigated using DFT(density functional theory)combined with the full potential linear augmented plane wave method and Monte Carlo simulations.The ground state of CoBr2...The intrinsic ferromagnetism of CoBr2 bulk was investigated using DFT(density functional theory)combined with the full potential linear augmented plane wave method and Monte Carlo simulations.The ground state of CoBr2 exhibits ferromagnetic behavior and a semiconductor character.We used the generalized gradient approximation(GGA)and GGA+U(Hubbard correction)approximations to determinate the magnetic moment.The magnetic moment reached the experimental value and was in good agreement with the other theoretical values.The value obtained was used as an input to a Monte Carlo study to calculate the thermal magnetization and magnetic hysteresis cycles.Ferromagnetic behavior was observed and was found to be due to an positive exchange interaction.These results lead us to believe that this material could be a promising spintronic material.展开更多
This work focuses on the ground-state phase diagram,the compensation temperatures and the critical behaviors of a ferrimagnetic graphene-like trilayer induced by crystal fields and exchange couplings.The simulation re...This work focuses on the ground-state phase diagram,the compensation temperatures and the critical behaviors of a ferrimagnetic graphene-like trilayer induced by crystal fields and exchange couplings.The simulation results show that a negative decrease in crystal field or an increase in exchange coupling can increase the critical temperature.More importantly,an M curve with double compensation temperatures can be observed,which is not predicted by the Neel theory.This remarkable compensation phenomenon has potential application value in the field of magnetic recording.展开更多
The magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic(AFM/FM)BiFeO_(3)/Co bilayer with mixed-spin(5/2,3/2)have been studied based on Monte Carlo simulation.The magnetization,susceptib...The magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic(AFM/FM)BiFeO_(3)/Co bilayer with mixed-spin(5/2,3/2)have been studied based on Monte Carlo simulation.The magnetization,susceptibility,and critical temperature are investigated under various exchange couplings and an external magnetic field.In particular,the influence of exchange couplings and an external magnetic field on the magnetic entropy change,adiabatic temperature change,and the relative cooling power(RCP)are studied.The simulation results indicated that the decrease of the exchange coupling and the increase of external magnetic fields can cause an increase of magnetic entropy change,adiabatic temperature change,and RCP.In addition,the hysteresis loops of the system are presented for different exchange couplings and temperatures.展开更多
The effect of particle size distribution on the field and temperature dependence of the hysteresis loop features like coercivity（HC）, remanence（MR）, and blocking temperature（TB） is simulated for an ensemble of s...The effect of particle size distribution on the field and temperature dependence of the hysteresis loop features like coercivity（HC）, remanence（MR）, and blocking temperature（TB） is simulated for an ensemble of single domain ferromagnetic nanoparticles with uniaxial anisotropy. Our simulations are based on the two-state model for T 〈 TB and the metropolis Monte-Carlo method for T 〉 TB. It is found that the increase in the grain size significantly enhances HC and TB. The presence of interparticle exchange interaction in the system suppresses HC but causes MRto significantly increase.Our results show that the parameters associated with the particle size distribution（D（d,δ）） such as the mean particle size d and standard-deviation δ play key roles in the magnetic behavior of the system.展开更多
The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Car...The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.展开更多
基金Project supported by the State Key Program of Basic Research of China （Grant No 2005CB623605）, the Natural Science Foundation of Fujian Province, China （Grant Nos E0320002 and 2005K020）, the National Natural Science Foundation of China （Grant No 10474037）.
文摘Based on Monte Carlo method, the oscillatory behaviour of the average magnetic moment as a function of the cluster sizes and the temperature dependences of magnetic moment with different sizes have been studied. It is found that the oscillations superimposed on the decreasing moment are associated with not only the geometrical structure effects but also the thermal fluctuation. The hystereses and thermal coercivities for free clusters with zero and finite uniaxial anisotropies have been calculated. The simulated thermal dependence of the coercivity is consistent with the experimental result, but does not fit the T^α law in the whole temperature range. It is evident that an easy magnetization direction and an anisotropy resulting from the spin configurations exist in the free clusters with the pure exchange interaction, which is also proved by the natural angle and energy distribution of clusters. A systematic theoretical analysis is also made to establish the relationship between natural angle and coercivity.
基金funded by the Project of Liaoning Education Department (No.LJKMZ20220500)the Natural Sciences Foundation of Liaoning province (Grant No.20230157)+1 种基金the National Natural Science Foundation of China (No.21976124)the Liaoning Revitalization Talents Program (No.XLYC2007195)。
文摘Using the Monte Carlo method,the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters such as crystal field,exchange coupling,external magnetic field,and temperature.The variations of magnetization,magnetic susceptibility,specific heat,and internal energy with the change of temperature are discussed.In addition,we also plot the phase diagrams including transition temperature and compensation temperature.Finally,multiple hysteresis loops under certain parameters are given.
文摘The intrinsic ferromagnetism of CoBr2 bulk was investigated using DFT(density functional theory)combined with the full potential linear augmented plane wave method and Monte Carlo simulations.The ground state of CoBr2 exhibits ferromagnetic behavior and a semiconductor character.We used the generalized gradient approximation(GGA)and GGA+U(Hubbard correction)approximations to determinate the magnetic moment.The magnetic moment reached the experimental value and was in good agreement with the other theoretical values.The value obtained was used as an input to a Monte Carlo study to calculate the thermal magnetization and magnetic hysteresis cycles.Ferromagnetic behavior was observed and was found to be due to an positive exchange interaction.These results lead us to believe that this material could be a promising spintronic material.
基金funded by National Natural Science Foundation of China (grant no. U22A20215)the Natural Science Foundation of Liaoning Province (grant no. 2023MS-218)
文摘This work focuses on the ground-state phase diagram,the compensation temperatures and the critical behaviors of a ferrimagnetic graphene-like trilayer induced by crystal fields and exchange couplings.The simulation results show that a negative decrease in crystal field or an increase in exchange coupling can increase the critical temperature.More importantly,an M curve with double compensation temperatures can be observed,which is not predicted by the Neel theory.This remarkable compensation phenomenon has potential application value in the field of magnetic recording.
文摘The magnetic properties and magnetocaloric effect of an antiferromagnetic/ferromagnetic(AFM/FM)BiFeO_(3)/Co bilayer with mixed-spin(5/2,3/2)have been studied based on Monte Carlo simulation.The magnetization,susceptibility,and critical temperature are investigated under various exchange couplings and an external magnetic field.In particular,the influence of exchange couplings and an external magnetic field on the magnetic entropy change,adiabatic temperature change,and the relative cooling power(RCP)are studied.The simulation results indicated that the decrease of the exchange coupling and the increase of external magnetic fields can cause an increase of magnetic entropy change,adiabatic temperature change,and RCP.In addition,the hysteresis loops of the system are presented for different exchange couplings and temperatures.
文摘The effect of particle size distribution on the field and temperature dependence of the hysteresis loop features like coercivity（HC）, remanence（MR）, and blocking temperature（TB） is simulated for an ensemble of single domain ferromagnetic nanoparticles with uniaxial anisotropy. Our simulations are based on the two-state model for T 〈 TB and the metropolis Monte-Carlo method for T 〉 TB. It is found that the increase in the grain size significantly enhances HC and TB. The presence of interparticle exchange interaction in the system suppresses HC but causes MRto significantly increase.Our results show that the parameters associated with the particle size distribution（D（d,δ）） such as the mean particle size d and standard-deviation δ play key roles in the magnetic behavior of the system.
文摘The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.
