Theoretical Study On The Magnetism-driven Ferroelectricity In The Low-dimensional Frustrated System

Multiferroic materials provide wide opportunities for the new type of data storage and magnetoelectric device on the basis of ferroelectricity-magnetism integrated effect due to its spontaneous magnetoelectric coupling effects. In recent years, the interest of investigation in this field is picked up again as the experimental technology and theoretical explored method are improved and consummated. Especially the multiferroic materials with frustrated structure have become a research focus for its abundant physical quantities and microscopic mechanisms. In this paper, we explore the magnetism and ferroelectricity in Ca3CoMnO6-type compound with the low-dimensional frustrated structure by using the one-dimensional elastic Ising model with the magnetic-phonon coupling with the consideration of nearest-neighbor FM and next-nearest-neighbor AFM interactions. According to the theoretical derivation and analysis, the decoupling between the lattice vibration and magnetic interaction is realized, and therefore the exact solutions of the physical quantities refleting the magnetic and ferroelectric properties of the Ca3CoMnO6-type compound are obtained by transfer-matrix method.The main works and conclusions are as follows:1. The magnetism and ferroelectricity in Ca3CoMnO6-type compound are investigated for the zero field. The curves for the magnetization, magnetic susceptibility, specific heat, polarization and relative dielectric constant are obtained, respectively. We analyze the cause for ferromagnetic Ising-like behavior in the magnetic susceptibility under zero field and the emergence of polarization, as well as the behavior of the relative dielectric constant. The broad peak on the dielectric constant curve indicates the short-range order.2. For different external magnetic fields, the magnetoelectric coupling effects in Ca3CoMnO6-type compound are explored. We have illustrated and disscussed the influence of magnetic field on the magnetization, magnetic susceptibility, specific heat polarization and relative dielectric constant of the system. The complex magnetic field dependence of polarization shown in the experimental data is not observed in our curve due to the interchain frustrated interaction and prominent anisotropy not taken into account in the present work.3.The magnetic and electric properties of the system for different next-nearest-neighbor exchange interaction under the magnetic field are investigated. We find the influence of different next-neareast-neighbor exchange interaction between Co ions on the magnetization, the magnetic susceptibility, the specific heat, the polarization and relative dielectric constant is not notable, except the shift of the peak and changes on the peak value. While for the various next-nearest-neighbor exchange striction between Mn ions, the magnetic susceptibility of the system exhibits the complex behavior in the low temperature. And the relative dielectric constant of the system is strengthened as well as the next-nearest-neighbor exchange striction between Mn ions increase. Besides, we analyzed the important role that the magnetic field have played in this process.