Role of non-thermal electrons in ultrafast spin dynamics of ferromagnetic multilayer
Je‐Ho Shim, Akbar Ali Syed, Jea-Il Kim, Hong‐Guang Piao, Sang-Hyuk Lee, Seung‐Young Park, Yeon Suk Choi, Kyung Min Lee, Hyun‐Joong Kim, Jong‐Ryul Jeong, Jung‐Il Hong, Dong Eon Kim, Dong‐Hyun Kim
Abstract
Understanding of ultrafast spin dynamics is crucial for future spintronic applications. In particular, the role of non-thermal electrons needs further investigation in order to gain a fundamental understanding of photoinduced demagnetization and remagnetization on a femtosecond time scale. We experimentally demonstrate that non-thermal electrons existing in the very early phase of the photoinduced demagnetization process play a key role in governing the overall ultrafast spin dynamics behavior. We simultaneously measured the time-resolved reflectivity (TR-R) and the magneto-optical Kerr effect (TR-MOKE) for a Co/Pt multilayer film. By using an extended three-temperature model (E3TM), the quantitative analysis, including non-thermal electron energy transfer into the subsystem (thermal electron, lattice, and spin), reveals that energy flow from non-thermal electrons plays a decisive role in determining the type I and II photoinduced spin dynamics behavior. Our finding proposes a new mechanism for understanding ultrafast remagnetization dynamics.