Mattern M, Pudell J-E, Laskin G, von Reppert A, Bargheer M
Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
Struct Dyn. 2021 Mar 24;8(2):024302. doi: 10.1063/4.0000072. eCollection 2021 Mar.
We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Grüneisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.
我们使用超快X射线衍射来研究膨胀声子应力和收缩磁应力对金属钙钛矿SrRuO薄膜在飞秒激光激发下皮秒应变响应的影响。我们举例说明了如何利用各向异性的体平衡热膨胀来预测薄膜对超快能量沉积的响应。需要注意的是，与近平衡热膨胀相比，横向均匀的激光激发会改变应变响应，因为平面内平衡应力在皮秒时间尺度上抑制了泊松应力。我们发现了一个非常大的负格林艾森常数，它描述了自旋系统中少量能量施加的大收缩应力。双脉冲激发方案下应变响应的温度和能量密度依赖性表明，在高能量密度 regime中磁应力达到饱和。
