Simultaneous control of ferromagnetism and ferroelasticity by oxygen octahedral backbone stretching

Coexistence of ferromagnetism and ferroelasticity in a single material is an intriguing phenomenon, but has been rarely found. Here we study both the ferromagnetism and ferroelasticity in a group of LaCoO3 films with systematically tuned atomic structures. We found that all films exhibit ferroelastic domains with four-fold symmetry and the larger domain size (higher elasticity) is always accompanied with stronger ferromagnetism. We performed synchrotron X-ray diffraction studies to investigate the backbone structure of the CoO6 octahedra, and found that both the ferromagnetism and the elasticity are simultaneously enhanced when the in-plane Co-O-Co bond angles are straightened. Therefore the study demonstrates the inextricable correlation between the ferromagnetism and ferroelasticity mediated through the octahedral backbone structure, which may open up new possibilities to develop multifunctional materials.