Coupled Magnetic-Ferroelectric Metal-Insulator Transition in Epitaxially Strained SrCoO3 from First Principles

First-principles calculations are presented for the epitaxial-strain dependence of the ground-state phase stability of perovskite SrCoO3. Through the combination of the large spin-phonon coupling with polarization-strain coupling and the coupling of the band gap to the polar distortion, both tensile and compressive epitaxial strain are seen to drive the bulk ferromagnetic-metallic (FM-M) phase to antiferromagnetic-insulating-ferroelectric (AFM-I-FE) phases, the latter having unusually low elastic energy. For compressive strain, there is a single coupled magnetic-ferroelectric metal-insulator transition. At this phase boundary, cross responses to applied electric and magnetic fields and stresses are expected. In particular, a magnetic field or compressive uniaxial stress applied to the AFM-FEz phase could induce an insulator-metal transition, and an electric field applied to the FM-M phase could induce a metal-insulator transition.