The interplay between structural, electronic and spin degrees of freedom at complex oxide heterointerfaces provides an exciting route to explore quantum materials with novel functional properties. Atomic-scale interactions at the interfaces between polar and non-polar transition metal oxides have led to the realization of exciting phenomena including two-dimensional electron gases, superconductivity and interfacial magnetism. However, these interactions may lead to the suppression of electronic and magnetic ordering at interfaces with strong structure-property relationships. By imaging the atomic structure of the interface between polar LaSrMnO₃ (LSMO) crystalline films and non-polar SrTiO₃, we identify interfacial structural distortions which are correlated with thickness-dependent metal-insulator and ferromagnetic-paramagnetic transitions in the rare-earth manganites. We show that these structural distortions can be tuned by inserting polarity-matched LaSrCrO₃ (LSCO) spacer layers at the LSMO interfaces leading to a stabilization of ferromagnetism in LSMO layers as thin as two unit cells. The stabilized magnetism is found to be independent of strain. We employ a combination of synchrotron X-ray diffraction, temperature-dependent magnetization measurements and X-ray magnetic circular dichroism to elucidate the interplay between structural and spin degrees of freedom in the rare-earth manganites.[1,2] Additionally, we find that by tuning growth and post-growth processing conditions, a two-dimensional electron gas (2DEG) forms at the interface between antiferromagnetic LaCrO₃ and SrTiO₃ providing a route to design all-oxide heterostructures which couple magnetic ordering with the mobile carriers within the 2DEG.[3] These results demonstrate the role of picometer-scale structural distortions on the physical properties of transition metal oxides and have important implications for designing novel quantum materials with functional properties including multiferroicity, metal-insulator transitions and tunable topological phases.

 References

 [1] Koohfar et. al., npj Quantum Materials 4 (1), 25 (2019)

[2] Koohfar et. al., Physical Review B 101 (6), 064420 (2020)

[3] Al-Tawhid et. al., AIP Advances 10 (4), 045132 (2020)