Material Science and Technology Division, Oak Ridge National Lab, Oak Ridge, Tennessee 37831, USA.
Department of Material Science and Engineering, Texas A&M University, College Station, Texas 77843, USA.
Phys Rev Lett. 2018 Jun 15;120(24):245701. doi: 10.1103/PhysRevLett.120.245701.
Shape memory strain glasses are frustrated ferroelastic materials with glasslike slow relaxation and nanodomains. It is possible to change a NiCoMnIn Heusler alloy from a martensitically transforming alloy to a nontransforming strain glass by annealing, but minimal differences are evident in the short- or long-range order above the transition temperature-although there is a structural relaxation and a 0.18% lattice expansion in the annealed sample. Using neutron scattering we find glasslike phonon damping in the strain glass but not the transforming alloy at temperatures well above the transition. Damping occurs in the mode with displacements matching the martensitic transformation. With support from first-principles calculations, we argue that the strain glass originates not with transformation strain pinning but with a disruption of the underlying electronic instability when disorder resonance states cross the Fermi level.
形状记忆应变玻璃是具有类玻璃缓慢弛豫和纳米畴的受挫铁弹性材料。通过退火，可以将 NiCoMnIn Heusler 合金从马氏体相变合金转变为非相变应变玻璃，但在相变温度以上，短程或长程有序几乎没有明显差异——尽管在退火样品中存在结构弛豫和 0.18%的晶格膨胀。通过中子散射，我们发现应变玻璃在远高于相变温度的温度下表现出类玻璃声子阻尼，但马氏体相变合金没有这种阻尼。阻尼发生在与马氏体相变相匹配的位移模式中。基于第一性原理计算，我们认为应变玻璃的起源不是相变应变钉扎，而是当无序共振态穿过费米能级时，基础电子不稳定性被破坏。
