Materials research involves primarily the study and manipulation of patterns, such as the lattice, spin, charge, and chemical composition structures, and their responses to changes in environmental condition or to external mechanical, magnetic, electric and chemical stimuli. Patterns occur in materials at all spatial length scales; at the atomic and nanoscale these patterns correspond to the atomic arrangements and electronic density patterns that make up the crystal structures, while at longer length scales these patterns correspond to the structural, magnetic, electric polarization and compositional domain patterns that constitute microstructures. Very often, design and development of new materials is reduced to the optimization of microstructures through processing or to the synthesis of artificial microstructures in composite and heterostructure materials. In this presentation, I will discuss the applications of the phase-field method to modeling and predicting the formation and stability of microstructural patterns in thin films and heterostructures. The focus will be on the thermodynamic stability of ferroic (ferroelectric, ferromagnetic and ferroelastic) domain patterns in ferroelectric and multiferroic thin films and nanoscale heterostructures, and their responses to applied local or uniform electric and mechanical stress and strain fields. I will also discuss the role of coupling among various order, such as electric polarization and oxygen octahedral rotation, in domain wall properties and domain patterns. In particular, I will show that the phase-field method may be used to not only interpret and understand experimentally observed domain patterns, but also provide guidance to synthesize and manipulate the domain patterns for optimum ferroelectric, piezoelectric or multiferroic responses.
An interview with Long-Qing Chen about his work and this talk is available here.