Extreme anti-reflection enhanced magneto-optic Kerr effect microscopy

• Published in: Nature communications Vol. 11; no. 1; pp. 5937 - 8
• Main Authors: Kim, Dongha, Oh, Young-Wan, Kim, Jong Uk, Lee, Soogil, Baucour, Arthur, Shin, Jonghwa, Kim, Kab-Jin, Park, Byong-Guk, Seo, Min-Kyo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.11.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/357/997; 639/301/930/2735; 639/624/1107/510; 639/624/400/1021; 639/624/400/1101; Amplitudes; Birefringence; Domain walls; Electron microscopy; Elementary excitations; Humanities and Social Sciences; Kerr effects; Kerr magnetooptical effect; Magnetic domains; Magnetic studies; Microscopy; multidisciplinary; Optical activity; Optics; Particle spin; Real time; Science; Science (multidisciplinary); Statistical analysis; Visibility; Wavelength
• DOI: 10.1038/s41467-020-19724-7
• ISSN: 2041-1723

Magnetic and spintronic media have offered fundamental scientific subjects and technological applications. Magneto-optic Kerr effect (MOKE) microscopy provides the most accessible platform to study the dynamics of spins, magnetic quasi-particles, and domain walls. However, in the research of nanoscale spin textures and state-of-the-art spintronic devices, optical techniques are generally restricted by the extremely weak magneto-optical activity and diffraction limit. Highly sophisticated, expensive electron microscopy and scanning probe methods thus have come to the forefront. Here, we show that extreme anti-reflection (EAR) dramatically improves the performance and functionality of MOKE microscopy. For 1-nm-thin Co film, we demonstrate a Kerr amplitude as large as 20° and magnetic domain imaging visibility of 0.47. Especially, EAR-enhanced MOKE microscopy enables real-time detection and statistical analysis of sub-wavelength magnetic domain reversals. Furthermore, we exploit enhanced magneto-optic birefringence and demonstrate analyser-free MOKE microscopy. The EAR technique is promising for optical investigations and applications of nanomagnetic systems. Magneto-optic Kerr effect microscopy is useful for dynamic magnetic studies, but is limited by the weak magneto-optical activity. Here, the authors show that extreme anti-reflection result in a Kerr amplitude as large as 20° and enables real-time detection of sub-wavelength magnetic domain reversals.