Lentfert Akira, De Anulekha, Scheuer Laura, Stadtmüller Benjamin, von Freymann Georg, Aeschlimann Martin, Pirro Philipp
Department of Physics and Research Centre OPTIMAS, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, 67663 Kaiserslautern, Germany.
Fraunhofer Institute for Industrial Mathematics ITWM, 67663 Kaiserslautern, Germany.
J Phys Condens Matter. 2024 Aug 12;36(45). doi: 10.1088/1361-648X/ad68b2.
The remagnetization process after ultrafast demagnetization can be described by relaxation mechanisms between the spin, electron, and lattice reservoirs. Thereby, collective spin excitations in form of spin waves and their angular momentum transfer play an important role on the longer timescales. In this work, we address the question whether the magnitude of demagnetization-the so-called quenching-affects the coherency and the phase of the excited spin waves. We present a study of coherent magnetization dynamics in thin nickel films after ultrafast demagnetization using the all-optical, time-resolved magneto-optical Kerr-effect technique. The largest coherent precession amplitude was observed for strongly quenched systems, indicating a well-defined precession phase for all pump pulses at a demagnetization of up to 90% in this system. Moreover, the phase of the excited spin-waves in Ni increases with the pump fluence, indicating a delayed start of the precession during the remagnetization. We compare these findings to recent studies in NiFe(permalloy), to evaluate the influence of the magneto-elastic coupling and non-linear spin-wave dynamics on the magnetization dynamics.
超快退磁后的再磁化过程可以用自旋、电子和晶格储能器之间的弛豫机制来描述。因此，自旋波形式的集体自旋激发及其角动量转移在较长时间尺度上起着重要作用。在这项工作中，我们探讨了退磁幅度（即所谓的猝灭）是否会影响激发自旋波的相干性和相位这一问题。我们使用全光、时间分辨磁光克尔效应技术，对超快退磁后的薄镍膜中的相干磁化动力学进行了研究。在强猝灭系统中观察到了最大的相干进动幅度，这表明在该系统中，对于所有泵浦脉冲，在高达90%的退磁情况下，进动相位都是明确的。此外，镍中激发自旋波的相位随泵浦通量增加，这表明在再磁化过程中进动开始延迟。我们将这些发现与最近关于镍铁（坡莫合金）的研究进行比较，以评估磁弹性耦合和非线性自旋波动力学对磁化动力学的影响。
