Journal
PHYSICAL REVIEW B
Volume 88, Issue 17, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.88.174426
Keywords
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Funding
- MURI-ARO [W911NF-07-1-0410]
- ONR [N00014-09-1-0302, N00014-12-1-1040]
- Center for Scientific Computing at the CNSI
- MRL: NSFMRSEC [DMR-1121053]
- NSF [CNS-0960316]
- Aspen Center for Physics (NSF) [1066293]
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First-principles calculations reveal a large cooperative coupling of Jahn-Teller (JT) distortion to oxygen-octahedron rotations in perovskite LaMnO3. The combination of the two distortions is responsible for stabilizing the strongly orthorhombic A-AFM insulating (I) ePbnm ground state relative to a metallic ferromagnetic (FM-M) phase. However, epitaxial strain due to coherent matching to a crystalline substrate can change the relative stability of the two states. In particular, coherent matching to a square-lattice substrate favors the less orthorhombic FM-M phase, with the A-AFM phase stabilized at higher values of tensile epitaxial strain due to its larger volume per formula unit, resulting in a coupled magnetic and metal-insulator transition at a critical strain close to 1%. At the phase boundary, a very large magnetoresistance is expected. Tensile epitaxial strain enhances the JT distortion and opens the band gap in the A-AFM-I c-ePbnm phase, offering the opportunity for band-gap engineering. Compressive epitaxial strain induces a transition within the FM-M phase from the c-ePbnm orientation to the ab-ePbnm orientation with a change in the direction of the magnetic easy axis relative to the substrate, yielding strain-controlled magnetization at the phase boundary. Similar behavior is expected in other JT active Pbnm perovskites.
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