Strain effects in low-dimensional transition metal oxides

Transition metal oxides offer a wide spectrum of properties which provide the foundation for a broad range of potential applications. Many of these properties originate from intrinsic coupling between lattice deformation and nanoscale electronic and magnetic ordering. Lattice strain thus has a profound influence on the electrical, optical, and magnetic properties of these materials. Recent advances in materials processing have led to the synthesis of low-dimensional single-crystal transition metal oxides, namely, epitaxial ultra-thin films and free-standing nano/microwires. Unlike bulk materials, these systems allow external tuning of uniform strain in these materials to tailor their properties and functionalities.This paper provides a comprehensive review of recent developments in studies of strain effects in transition metal oxide ultra-thin films and nano/microwires. In epitaxial thin films, biaxial strain is developed as a result of lattice mismatch between the film and the substrate. By choosing different substrates, a wide range of strain can be established at discrete values that allows for exploration of new phase space, enhancement of order parameters, creation of complicated domain textures, and stabilization of new phases. On the other hand, continuous tuning of uniaxial strain is possible in nano/microwires, where a variety of phase transitions and their dynamics could be probed at the single or few-domain scale. We focus on the work of strain-controlled electromechanical response in piezoelectric oxides and strain-induced metal–insulator transitions as well as domain physics in strongly correlated electron oxides. Related nanoscale device applications such as strain sensing and power generation will be highlighted as well.