Theoretical calculation study of magnetism and ferroelectricity

Report title: Theoretical calculation research on magnetism and ferroelectricity

Report summary:

Magnetic materials and ferroelectric materials have broad application prospects in the field of information storage and processing. In this report I will introduce our work combining first-principles calculations and theoretical modeling to study the magnetism and ferroelectricity of materials. Specifically, we will first introduce the effective Hamiltonian method (including the "four-state method" and machine learning method for constructing Hamiltonian), as well as our recently developed material property calculation and simulation software package PASP. We will then introduce the application of our methods and procedures to some magnetic and ferroelectric systems (including multiferroic systems where magnetism and ferroelectricity coexist). For example, we developed a unified polarization model for spin order-induced ferroelectricity, and based on the model and method, we understood the microscopic mechanism of ferroelectricity in the second type of multiferroic materials; we found that strong high-order magnetic interactions may exist in two-dimensional systems, which is beneficial to improving the stability of ferromagnetic states; we found that large non-polar molecules may induce ferroelectricity; we proposed a new mechanism for using electric fields to control the topological magnetic order charge sign of multiferroic systems, etc.

Personal profile:

Xiang Hongjun is a professor in the Department of Physics at Fudan University. He studied at the University of Science and Technology of China from 1997 to 2006 and received his bachelor's and doctoral degrees. From 2006 to 2009, he conducted research as a postdoctoral fellow at North Carolina State University and the U.S. Renewable Energy National Laboratory. Professor Xiang Hongjun is engaged in computational condensed matter physics research and has made progress in the establishment of multiferroic physics models and the development of computational methods. Representative achievements include: Proposing a universal model of spin order-induced ferroelectricity, breaking through the limitations of traditional models, and providing a general physical image of a large class of multiferroics, which has been recognized by experts in the field. A four-state method for calculating magnetic interaction and magnetoelectric coupling strength was established. This method has been widely used by domestic and foreign research groups. Based on these models and methods, he explained the origin of ferroelectricity in multiferroic materials and discovered new magnetoelectric coupling mechanisms; designed high-performance multiferroic materials, and some predictions have been confirmed by experiments; and developed the material property analysis and simulation software package PASP. Relevant research results have been published in Phys. Rev. Lett., Nature Mater., Nature Comm., Phys. Rev. X and other magazines as the first/corresponding author. Published more than 200 papers, including 30 Phys. Rev. Lett. Since 2014, he has been continuously selected as a Highly Cited Scholar in China by Elsevier. In 2018, he was funded by the National Natural Science Foundation of China's Outstanding Youth Science Fund, and won the ICTP Award from the Italian International Center for Theoretical Physics. In 2021, he was selected as an APS fellow of the American Physical Society.