近日，中国科学院物理研究所金奎娟团队研究了光学二次谐波发生定量表征G型反铁磁性。该项研究成果发表在2025年4月22日出版的《光：科学与应用》杂志上。

反铁磁性因其热稳定性、低能耗和快速开关速度而成为下一代电子器件的有前景的候选者。然而，反铁磁序中净磁矩的消除对定量表征和调制提出了巨大挑战，阻碍了其研究和应用。在这项工作中，研究组利用宽温度范围内的光学二次谐波发生（SHG）、集成微分相衬扫描透射电子显微镜和第一性原理计算，对BiFeO₃薄膜中非共线反铁磁有序在一系列应变下的演化进行了定量研究。

结果发现，反铁磁耦合显著增强，其特征是Néel温度从428 K升高到646 K，应变操纵使G型反铁磁阶的SHG强度提高了一个数量级，从-2.4%提高到+0.6%。研究组将反铁磁耦合的增强归因于当平面晶格常数增加时，当Fe-O-Fe键角接近180°时，超交换相互作用的增强，这也可能导致从非共线反铁磁顺序到共线顺序的趋势。该工作不仅弥合了外延多铁性中的反铁磁序和应变操纵，更重要的是，还为SHG技术的定量表征和反铁磁性的精确操纵铺平了道路。

附：英文原文

Title: Characterizing G-type antiferromagnetism quantitatively with optical second harmonic generation

Author: Xu, Shuai, Ma, Cheng, Jin, Kui-juan, Zhang, Qinghua, Huang, Sisi, Wang, Yiru, He, Xu, Wang, Jiesu, Xie, Donggang, Zhang, Qiulin, Guo, Er-Jia, Ge, Chen, Wang, Can, Xu, Xiulai, Gu, Lin, He, Meng, Yang, Guozhen

Issue&Volume: 2025-04-22

Abstract: Antiferromagnetism has become a promising candidate for the next generation electronic devices due to its thermal stability, low energy consumption, and fast switching speed. However, the canceling of the net magnetic moment in antiferromagnetic order presents great challenge on quantitative characterization and modulation, hindering its investigation and application. In this work, utilizing the optical second harmonic generation (SHG) in a wide temperature range, the integrated differential phase contrast scanning transmission electron microscopy, and first-principles calculations, we performed a quantitative study on the evolution of non-collinear antiferromagnetic order in BiFeO3 films with a series of strains. We found that the antiferromagnetic coupling was significantly enhanced, featured by the increase of Néel temperature from 428K to 646K, and by one order of enhancement of SHG intensity contributed from the G-type antiferromagnetic order by strain manipulation from -2.4% to +0.6%. We attributed the enhancement of the antiferromagnetic coupling to the enhancement of the superexchange interaction as the Fe-O-Fe bond angle approaches 180° when the in-plane lattice constants increase, which might also result in a tendency from a non-collinear antiferromagnetic order to a collinear one. Our work not only bridges the antiferromagnetic order and the strain manipulation in epitaxial multiferroics, more importantly, also paves a way for quantitative characterization by SHG technology and the precise manipulation of antiferromagnetism.

DOI: 10.1038/s41377-025-01849-3

Source: https://www.nature.com/articles/s41377-025-01849-3