A theoretical approach is generalized and employed in this work to evaluate the magnetoresistivity of ErBi in external magnetic fields. The calculated results and theoretical analyses show that when an external magnet...A theoretical approach is generalized and employed in this work to evaluate the magnetoresistivity of ErBi in external magnetic fields. The calculated results and theoretical analyses show that when an external magnetic field is applied in the z-direction, the magnetoresistivity can be reduced considerably due to the degeneracy lifting of the crystal-field levels. However, when the magnetic field is exerted along the x-axis, the magnetoresistivity will be increased because of the formations of new magnetic states of the Er ion and its transitions within and between these new states.展开更多
A theoretical approach is generalized and employed to calculate the magneto-resistivity of a rare-earth crystalline （CeAh） with degenerate ground crystal-field （CF） level in the presence of external fields. The ca...A theoretical approach is generalized and employed to calculate the magneto-resistivity of a rare-earth crystalline （CeAh） with degenerate ground crystal-field （CF） level in the presence of external fields. The calculated results show that when a magnetic field is applied in the c-direction, the magneto-resistivity may be reduced by more than 90% in certain cases in comparison with the pure CF contribution at the same temperature, demonstrating the strong effects of the degeneracy removals of the CF levels on the magnetic resistivity.展开更多
We employ a two-ion model to calculate the spontaneous magnetization and susceptibility of TbNi2B2C with the mean-field theory, and derive an analytic formula for the Néel temperature of the material with the per...We employ a two-ion model to calculate the spontaneous magnetization and susceptibility of TbNi2B2C with the mean-field theory, and derive an analytic formula for the Néel temperature of the material with the perturbation theory. In both the cases, only the four lowest crystal-electric-field （CEF） states are taken into account as base functions. Our theoretical results are consistent with the experimental data, manifesting the strong effects of the low lying CEF states on the magnetic behaviors of the material and the suitability of the theoretical approach proposed here.展开更多
Among rare-earth compounds, there are many materials having non-magnetic crystal-field （CF） ground levels. To understand their magnetic behaviour at low temperatures, we study the effects of the CF levels and the He...Among rare-earth compounds, there are many materials having non-magnetic crystal-field （CF） ground levels. To understand their magnetic behaviour at low temperatures, we study the effects of the CF levels and the Heisenberg-like coupling on the magnetic process of such a crystalline with mean-field and CF theory. It is found that the material can be magnetically ordered if the Heisenberg exchange is sufficiently strong. Additionally we obtain a condition for initial magnetic ordering, and derive a formula for estimating the Curie temperature if the ordering occurs.展开更多
A two-sublattice model for rare-earth emtiferromagnets is employed to study the magnetic properties of TbNi2B2 （2. The theoretical susceptibility and magnetization curves obtained with the model show reasonable agree...A two-sublattice model for rare-earth emtiferromagnets is employed to study the magnetic properties of TbNi2B2 （2. The theoretical susceptibility and magnetization curves obtained with the model show reasonable agreement with the experimental results.展开更多
The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3𝑒ions which are ...The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3𝑒ions which are coupled antiferromagnetically.In the absence of the external magnetic field,all simulations are started from a spin configuration with all moments in the nanosample randomly oriented and performed from a temperature above the magnetic transition temperature𝑈M down to very low temperature as carried out by previous researchers using the Monte Carlo method,and such obtained results are all physically reasonable,verifying the correctness of the simulation model and computing algorithm.In addition,our calculated results suggest that increasing the surface anisotropy enables an increase in the magnetic transition temperature,although less effectively than by enhancing the Heisenberg exchange strength directly.展开更多
A Usov-type quantum model based on a mean-field approximation is utilized to simulate the magnetic structure of an assumed rare-earth nanoparticle consisting of an antiferromagnetic core and a paramagnetic outer shell...A Usov-type quantum model based on a mean-field approximation is utilized to simulate the magnetic structure of an assumed rare-earth nanoparticle consisting of an antiferromagnetic core and a paramagnetic outer shell.We study the magnetic properties in the presence and absence of an external magnetic field.Our simulation results show that the magnetic moments in the core region orientate antiferromagnetically in zero external magnetic field;an applied magnetic field rotates all of the magnetic moments in the paramagnetic shell completely to the field direction,and turns those in the core(which tries to maintain its original antiferromagnetic structure)towards the orientation in some degree;and the paramagnetic shell does not have a strong influence on the magnetic configuration of the core.展开更多
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK2008438, and the Research Plan MSM of the Ministry of Education of the Czech Republic under Grant No 0021620834.
文摘A theoretical approach is generalized and employed in this work to evaluate the magnetoresistivity of ErBi in external magnetic fields. The calculated results and theoretical analyses show that when an external magnetic field is applied in the z-direction, the magnetoresistivity can be reduced considerably due to the degeneracy lifting of the crystal-field levels. However, when the magnetic field is exerted along the x-axis, the magnetoresistivity will be increased because of the formations of new magnetic states of the Er ion and its transitions within and between these new states.
文摘A theoretical approach is generalized and employed to calculate the magneto-resistivity of a rare-earth crystalline （CeAh） with degenerate ground crystal-field （CF） level in the presence of external fields. The calculated results show that when a magnetic field is applied in the c-direction, the magneto-resistivity may be reduced by more than 90% in certain cases in comparison with the pure CF contribution at the same temperature, demonstrating the strong effects of the degeneracy removals of the CF levels on the magnetic resistivity.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK2008438, and the Ministry of Education of the Czech Republic under Grant No MSM-0021620834.
文摘We employ a two-ion model to calculate the spontaneous magnetization and susceptibility of TbNi2B2C with the mean-field theory, and derive an analytic formula for the Néel temperature of the material with the perturbation theory. In both the cases, only the four lowest crystal-electric-field （CEF） states are taken into account as base functions. Our theoretical results are consistent with the experimental data, manifesting the strong effects of the low lying CEF states on the magnetic behaviors of the material and the suitability of the theoretical approach proposed here.
文摘Among rare-earth compounds, there are many materials having non-magnetic crystal-field （CF） ground levels. To understand their magnetic behaviour at low temperatures, we study the effects of the CF levels and the Heisenberg-like coupling on the magnetic process of such a crystalline with mean-field and CF theory. It is found that the material can be magnetically ordered if the Heisenberg exchange is sufficiently strong. Additionally we obtain a condition for initial magnetic ordering, and derive a formula for estimating the Curie temperature if the ordering occurs.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK2008438, and the Ministry of Education of the Czech Republic under Grant No MSM 0021620834.
文摘A two-sublattice model for rare-earth emtiferromagnets is employed to study the magnetic properties of TbNi2B2 （2. The theoretical susceptibility and magnetization curves obtained with the model show reasonable agreement with the experimental results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274177,1105075,1104146,10804053 and 11047143.
文摘The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3𝑒ions which are coupled antiferromagnetically.In the absence of the external magnetic field,all simulations are started from a spin configuration with all moments in the nanosample randomly oriented and performed from a temperature above the magnetic transition temperature𝑈M down to very low temperature as carried out by previous researchers using the Monte Carlo method,and such obtained results are all physically reasonable,verifying the correctness of the simulation model and computing algorithm.In addition,our calculated results suggest that increasing the surface anisotropy enables an increase in the magnetic transition temperature,although less effectively than by enhancing the Heisenberg exchange strength directly.
基金by the Natural Science Foundation of Jiangsu Province under Grant No BK2008438the Ministry of Education of the Czech Republic under Grant No MSM 0021620834.
文摘A Usov-type quantum model based on a mean-field approximation is utilized to simulate the magnetic structure of an assumed rare-earth nanoparticle consisting of an antiferromagnetic core and a paramagnetic outer shell.We study the magnetic properties in the presence and absence of an external magnetic field.Our simulation results show that the magnetic moments in the core region orientate antiferromagnetically in zero external magnetic field;an applied magnetic field rotates all of the magnetic moments in the paramagnetic shell completely to the field direction,and turns those in the core(which tries to maintain its original antiferromagnetic structure)towards the orientation in some degree;and the paramagnetic shell does not have a strong influence on the magnetic configuration of the core.
