Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, USA.
Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA.
Phys Rev Lett. 2014 Mar 28;112(12):126401. doi: 10.1103/PhysRevLett.112.126401. Epub 2014 Mar 26.
A dynamical method is introduced to study the effect of dimensionality on phase transitions. Direct experimental measurements for the lower critical dimension for spin glasses is provided as an example. The method makes use of the spin glass correlation length ξ(t,T). Once nucleated, it can become comparable to sample dimensions in convenient time and temperature ranges. Thin films of amorphous Ge:Mn alloys were prepared with thickness L≈15.5 nm. Conventional behavior is observed as long as ξ(t,T)<L. At the measurement time tco, when ξ(tco,T)≈L, the time dependence is observed to cross over to exponential. These results are interpreted using spin glass dynamics, and are consistent with a lower critical dimension for spin glasses, dℓ, between 2<dℓ<3.
一种动力学方法被引入来研究维度对相变的影响。以自旋玻璃为例，提供了对低临界维度的直接实验测量。该方法利用自旋玻璃相关长度 ξ(t,T)。一旦被引发，它可以在方便的时间和温度范围内与样品尺寸相当。用厚度 L≈15.5 nm 制备了非晶 Ge:Mn 合金的薄膜。只要 ξ(t,T)<L，就可以观察到常规行为。在测量时间 tco 处，当 ξ(tco,T)≈L 时，观察到时间依赖性跃迁到指数。这些结果使用自旋玻璃动力学进行解释，并且与自旋玻璃的低临界维度 dℓ，2<dℓ<3 一致。
