Department of Physics, Ernst-Moritz-Arndt-University, 17489, Greifswald, Greifswald, Germany.
Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-75120, Uppsala, Sweden.
Sci Rep. 2017 Jun 23;7(1):4114. doi: 10.1038/s41598-017-04167-w.
Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles. We show that the magnetisation switching is a stochastic process. We develop a complete multiscale model which allows us to optimize the number of laser shots needed to switch the magnetisation of high anisotropy FePt nanoparticles in our experiments. We conclude that only angular momentum induced optically by the inverse Faraday effect will provide switching with one single femtosecond laser pulse.
利用超短激光脉冲来操控磁化是有前途的信息存储设备应用。磁化响应的动力学取决于初始激光激发过程中光子向自旋的能量转移。对于磁性存储，FePt 纳米粒子是一种特别感兴趣的材料，最近已经证明了其通过光学轨道角动量来切换磁化。其机制尚不清楚。在这里，我们通过实验和理论研究了 FePt 纳米粒子的全光学切换。我们表明，磁化切换是一个随机过程。我们开发了一个完整的多尺度模型，使我们能够优化在实验中切换具有高各向异性的 FePt 纳米粒子的磁化所需的激光脉冲数。我们的结论是，只有通过逆法拉第效应光诱导的轨道角动量才能提供单次飞秒激光脉冲的切换。
