Domain glasses: Twin planes, Bloch lines, and Bloch points

• Published in: physica status solidi (b) Vol. 252; no. 12; pp. 2639 - 2648
• Main Authors: Salje, E. K. H., Carpenter, M. A.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.12.2015
• Subjects: domain boundaries; domain glasses; ferroelastic materials; multiferroics
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201552430

Ferroelastic materials can develop complex domain structures, which have properties of glassy systems (non‐ergodicity, glass dynamics, glass transitions, and freezing). Four characteristic temperatures are defined for such domain glasses: the dynamical nucleation temperature Td where local correlated clusters can form glass states within a (tweed‐) nano structure, To the Vogel–Fulcher temperature of these precursor nano‐structures, Tpt the phase transition temperature where the (ferroelastic) transition occurs, and TK the Kauzmann temperature where the complex domain structure freezes. Td exists in most ferroelastic materials whereas the other transitions depend on the complexity of the domain patterns and hence on their thermal history. Shear collapse and rapid thermal quench of ferroelastic crystals preferentially lead to domain glasses whereas slow anneal produces mostly highly correlated pattern such as stripe patterns or single domain crystals. Domain glasses are compared with structural glasses and several examples for domain glass features are discussed. Complex domain configurations can form glass states with four characteristic temperatures: Td – nucleation temperature of local twins and tweed, To – onset of coherency, Tpt – structural transition with extended domain structures, and TK – domains freezing. Characteristic dynamical structures include Bloch lines between ferroelectric domains (see figure) where the polar axis rotates between domains. Rotations with opposite chirality coincide inside a Bloch wall (middle of the figure) and form a Bloch point. In this article, Salje and Carpenter compare domain glasses with structural glasses, and several examples for domain glass features are discussed.