Song Lijian, Xu Wei, Huo Juntao, Li Fushan, Wang Li-Min, Ediger M D, Wang Jun-Qiang
CAS Key Laboratory of Magnetic Materials and Devices, and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Rev Lett. 2020 Sep 25;125(13):135501. doi: 10.1103/PhysRevLett.125.135501.
As opposed to the common monotonic relaxation process of glasses, the Kovacs memory effect describes an isothermal annealing experiment, in which the enthalpy and volume of a preannealed glass first increases before finally decreasing toward equilibrium. This interesting behavior has been observed for many materials and is generally explained in terms of heterogeneous dynamics. In this Letter, the memory effect in a model Au-based metallic glass is studied using a high-precision high-rate calorimeter. The activation entropy (S^{}) during isothermal annealing is determined according to the absolute reaction rate theory. We observe that the memory effect appears only when the second-annealing process has a large S^{}. These results indicate that a large value of S^{*} is a key requirement for observation of the memory effect and this may provide a useful perspective for understanding the memory effect in both thermal and athermal systems.
与玻璃常见的单调弛豫过程不同，科瓦奇记忆效应描述了一种等温退火实验，在该实验中，预退火玻璃的焓和体积在最终趋向平衡而减小之前首先增加。这种有趣的行为已在许多材料中观察到，并且通常根据非均匀动力学来解释。在本快报中，使用高精度高速量热仪研究了一种基于金的模型金属玻璃中的记忆效应。根据绝对反应速率理论确定等温退火过程中的活化熵（S*）。我们观察到，只有当第二次退火过程具有较大的S时，记忆效应才会出现。这些结果表明，较大的S值是观察记忆效应的关键条件，这可能为理解热系统和非热系统中的记忆效应提供一个有用的视角。
