二维铁磁半导体理论与实验进展

Theoretical and experimental progress of two-dimensional ferromagnetic semiconductors

大数据时代对海量电子信息的非易失性高效存储和处理的需求,催生了自旋电子学这门新兴学科.作为新型功能化自旋电子器件的核心构成材料,铁磁半导体因其独特的磁电特性而受到了广泛的关注.近年来,二维材料的发现更是为铁磁半导体的发展开创了新的舞台.本文主要针对二维铁磁半导体的室温磁序稳定性问题,以近年来备受关注的CrGeTe3、CrI3等典型的二维磁性半导体为例,介绍了二维铁磁半导体在实验与理论方面的主要研究进展,着重介绍了二维铁磁半导体中磁耦合(自旋相互作用)的理论模型,以及增强铁磁耦合、提升居里温度的基本机制,同时讨论了磁各向异性对二维长程铁磁序的重要意义.最后,从p电子磁性和低能耗电控磁两个方面,展望了二维铁磁半导体的未来发展.希望本文可以帮助读者更好地了解二维铁磁半导体领域的发展近况,给读者带来一些启发.

In the era of big data,the demand for non-volatile and efficient storage and processing of massive electronic information has promoted the rapid development of electronic information technology.As the core material of transistors,semiconductor materials are widely used in various electronic devices.However,due to the increasingly significant“heat dissipation”and“quantum tunneling”effect of traditional semiconductor devices at the nanoscale,it is difficult to meet people’s demand for more miniaturized electronic information equipment.Therefore,it is urgent to develop new functional semiconductor materials.The appearance of magnetoresistance information storage technology makes people pay more attention to the magnetic properties of devices.At the same time,spintronics,which is a new discipline,is developed to study the correlation between electron charges and spin properties.As the core material of new functional spintronic devices,ferromagnetic semiconductors have attracted wide attention due to their unique magnetoelectric properties.In recent years,the discovery of two-dimensional ferromagnetic materials has opened a new stage for the development of ferromagnetic semiconductors.However,according to Mermin-Wagner’s theory,due to the strong thermal fluctuations in two-dimensional materials at finite temperatures,a two-dimensional system with long-range magnetic order has been thought to be non-existent.It is found that the effect of thermal fluctuation on magnetic order can be offset by the magnetic anisotropy of the system.Moreover,it is found that there is an inherent long-range magnetic order in the two-dimensional CrGeTe3 and CrI3 structures.This provides a platform for the research of two-dimensional magnetic semiconductors.In this review,we focus on the room temperature magnetic order stability of two-dimensional ferromagnetic semiconductors,taking CrGeTe3,CrI3,and other typical two-dimensional magnetic semiconductors as examples,to introduce the recent experimental progress of two-dimensional ferromagnetic semiconductors.At the same time,in the theoretical research,this paper introduces the two-dimensional magnetic semiconductors and their magnetic properties discovered by structural search and design in recent years.The existing two-dimensional magnetic semiconductor is modified by surface adsorption,charge doping and stress application.Based on the two-orbit model based on the tightly bound approximation,the Curie temperature can be increased by enhancing the ferromagnetic exchange interaction and weakening the antiferromagnetic exchange interaction,and the significance of magnetic anisotropy is discussed.Finally,we briefly prospect the future development of two-dimensional ferromagnetic semiconductors from two aspects of p electron magnetism and low energy consumption electronic magnetic control.It is hoped that this review will enlighten people to understand two-dimensional ferromagnetic semiconductors and magnetic coupling mechanism comprehensively.