Evidence for broken ergodicity in strain glass

A recent study has indicated that there exists a different class of glass, the strain glass, in the nontransforming composition regime of Ti-Ni alloys. However, the critical proof for a glass, the evidence for the nonergodicity in the glassy state, has been missing in this system. By a zero-field-cooling/field-cooling measurement of static strain, we show experimentally that the ergodicity of the frozen strain glass is indeed broken. The creep measurement clearly shows the slowing down of kinetics upon strain glass transition. These features are physically parallel to other well-known glasses such as cluster-spin glasses and ferroelectric relaxors; thus, we introduce the notion of a ferroic glass and suggest a common underlying physics.