Investigation Of Magnetism Of Ca₃Co₂O₆ At Low Temperature By Monte Carlo Simulation

Jumping-steps emerged at low temperature in magnetization curve of compound Ca₃Co₂O₆ cannot be observed in most other magnetic materials,which has been a new bring spot in the field of magnetic storage technology and magnetic theory.In the last decade sorts of investigation had been made about its magnetic attribute at low temperature,arranging from microscale to macroscale,experiment to calculation,and theory to simulation.There are several model about the origination of steps emerged in the magnetization curve.For the sake of discussing the cause why steps appears in the magnetization curve at low temperature and how the shape of magnetization curve alters at different condition,this article makes use of Monte Carlo simulation technology to carry through a research on Ca₃Co₂O₆.The main results are as follows:(1) The three-dimensional Ising model designed in the article is constructed by cobalt-oxygen chain,which is the element of triangular configuration.This 3d model reflects unfeignedly symmetry of R(?)c space group of Ca₃Co₂O-6 lattice,which makes the simulation results exhibit the physical essence of jump in the magnetization curve;Meanwhile,introducing of n-Fold method that belongs to a class of methods called 'event-driven Monte Carlo',speeds up the simulation process enormously,increases the efficiency of sample at low temperature especially,and makes the simulation of 3d model be carried out.(2) In the 3d Ising model,several phenomena observed in experiments recur in simulation results.For instance,as temperature drops below 25 K a big plateau with width of 3.6 T and height of M_s/3 comes forth in the magnetization curve,as well as temperature below 10 K the big plateau were divided into three substeps of equal-width.It is found that plateau of height of M_s/3 takes on the lowest energy in the simulation results,and magnetization curves of different simulation processes vary greatly.(3) As is different from the 2d model simulation results but consistent with experiments, substeps may both emerge and merge in the magnetization curve of 3d model,as long as simulation time at different applied field is adjusted and prolonged.Substeps can merge and only can a plateau of height of M_s/3.These results show that emergence of substeps attributes to non-equilibrium relaxation.Magnetization has a long relaxation time,and is correlated with idiographic measure process.