Relaxation processes are decisive for many physical properties of amorphous materials. For amorphous phase-change materials (PCMs) used in nonvolatile memories, relaxation processes are, however, difficult to characterize because of the lack of bulk samples. Here, instead of bulk samples, we use powder mechanical spectroscopy for powder samples to detect the prominent excess wings-a characteristic feature of β-relaxations-in a series of amorphous PCMs at temperatures below glass transitions. By contrast, β-relaxations are vanishingly small in amorphous chalcogenides of similar composition, which lack the characteristic features of PCMs. This conclusion is corroborated upon crossing the border from PCMs to non-PCMs, where β-relaxations drop substantially. Such a distinction implies that amorphous PCMs belong to a special kind of covalent glasses whose locally fast atomic motions are preserved even below the glass transitions. These findings suggest a correlation between β-relaxation and crystallization kinetics of PCMs, which have technological implications for phase-change memory functionalities.

中文翻译：

---

在非晶相变材料中发现β松弛。

弛豫过程对非晶材料的许多物理性质起决定性作用。但是，对于非易失性存储器中使用的非晶相变材料（PCM），由于缺乏大量样本，因此难以表征松弛过程。在这里，代替散装样品，我们使用粉末机械光谱学对粉末样品进行检测，以检测低于玻璃化转变温度的一系列非晶态PCM中显着的过量机翼（β弛豫的特征）。相反，在相似组成的无定形硫族化物中，β-松弛非常小，而缺乏PCM的特征。当从PCM跨越到非PCM的边界时，这一结论得到了证实，其中β松弛显着下降。这种区别意味着非晶态PCM属于一种特殊的共价玻璃，即使在玻璃化转变温度以下，其局部快速原子运动也得以保留。这些发现表明，β-松弛与PCM的结晶动力学之间具有相关性，这对相变存储功能具有技术意义。