Imaging and control of critical fluctuations in two-dimensional magnets

• Published in: Nature materials 2020-12, Vol.19 (12), p.1290-1294
• Main Authors: Jin, Chenhao, Tao, Zui, Kang, Kaifei, Watanabe, Kenji, Taniguchi, Takashi, Mak, Kin Fai, Shan, Jie
• Format: Article
• Language: English
• Subjects: 639/301/357/1018; 639/766/119/997; Biomaterials; Chemistry and Materials Science; Chromium bromides; Condensed Matter Physics; Correlation; Critical phenomena; Critical point; Feedback control; Ferromagnetism; Fluctuations; Imaging; Imaging techniques; Letter; Magnetic materials; Magnetic permeability; Magnetic variations; Magnetization; Magnets; Materials Science; Nanotechnology; Neutron scattering; Optical and Electronic Materials; Phase transitions; Real time; Stability
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-020-0706-8

Strong magnetization fluctuations are expected near the thermodynamic critical point of a continuous magnetic phase transition. Such critical fluctuations are highly correlated and in principle can occur at any time and length scales 1 ; they govern critical phenomena and potentially can drive new phases 2 , 3 . Although critical phenomena in magnetic materials have been studied using neutron scattering, magnetic a.c. susceptibility and other techniques 4 – 6 , direct real-time imaging of critical magnetization fluctuations remains elusive. Here we develop a fast and sensitive magneto-optical imaging microscope to achieve wide-field, real-time monitoring of critical magnetization fluctuations in single-layer ferromagnetic insulator CrBr 3 . We track the critical phenomena directly from the fluctuation correlations and observe both slowing-down dynamics and enhanced correlation length. Through real-time feedback control of the critical fluctuations, we further achieve switching of magnetic states solely by electrostatic gating. The ability to directly image and control critical fluctuations in 2D magnets opens up exciting opportunities to explore critical phenomena and develop applications in nanoscale engines and information science. The development of a magneto-optical imaging technique enables the real-time imaging and control of critical magnetic fluctuations in the single-layer ferromagnetic insulator CrBr 3 .