Controllable conduction and hidden phase transitions revealed via vertical strain

The desire for room-temperature multiferroicity has motivated the search for hidden phase transitions at higher temperatures. By means of the imposition of vertical strain in EuTiO3 (ETO)–MgO nanocomposite films, we unveil two hidden phase transitions in the strained ETO phase at around T′ = 80 K and T* = 230 K, and we are able to tune the behavior of the electrical conductivity at these temperatures. Compared with the phase transition temperatures in bulk ETO, T′ remains unchanged and T* is increased owing to stretching of the c-axis lattice. Interface-limited conduction appears at both transitions, in contrast to the bulk-limited mode shown at other temperatures. With regard to the underlying mechanism, it is found that controllable behavior of conduction at the transition temperatures can be achieved by the common effect of vertical strain and oxygen vacancies. Overall, the present work highlights the importance of the effect of vertical strain in revealing and enhancing the tunability of properties at hidden phase transitions.The desire for room-temperature multiferroicity has motivated the search for hidden phase transitions at higher temperatures. By means of the imposition of vertical strain in EuTiO3 (ETO)–MgO nanocomposite films, we unveil two hidden phase transitions in the strained ETO phase at around T′ = 80 K and T* = 230 K, and we are able to tune the behavior of the electrical conductivity at these temperatures. Compared with the phase transition temperatures in bulk ETO, T′ remains unchanged and T* is increased owing to stretching of the c-axis lattice. Interface-limited conduction appears at both transitions, in contrast to the bulk-limited mode shown at other temperatures. With regard to the underlying mechanism, it is found that controllable behavior of conduction at the transition temperatures can be achieved by the common effect of vertical strain and oxygen vacancies. Overall, the present work highlights the importance of the effect of vertical strain in revealing and enhancing the tunability of properties at...