Predicting hidden bulk phases from surface phases in bilayered Sr3Ru2O7

Abstract

The ability to predict hidden phases under extreme conditions is not only crucial to understanding and manipulating materials but it could also lead to insight into new phenomena and novel routes to synthesize new phases. This is especially true for Ruddlesden-Popper perovskite phases that possess interesting properties ranging from superconductivity and colossal magnetoresistance to photovoltaic and catalytic activities. In particular, the physical properties of the bilayer perovskite Sr3Ru2O7 at the surface are intimately tied to the rotation and tilt of the RuO6 octahedra. To take advantage of the extra degree of freedom associated with tilting we have performed first principles hybrid density functional simulations of uniaxial pressure applied along the c-axis of bulk Sr3Ru2O7 where we find that the octahedra become tilted, leading to two phase transitions. One is a structural transition at 1.5 GPa, and the other is from a ferromagnetic (FM) metal to an antiferromagnetic (AFM) insulator at 21 GPa whose AFM spin configuration is different from the AFM state near the FM ground state.

Half-metallic ferromagnetism in Sr3Ru2O7

“…However, more studies are needed to understand how distortions couple with the electronic and magnetic properties in Sr 3 Ru 2 O 7 as our recent work on octahedra tilts. 53…”

Revealing out-of-equilibrium hidden phases in Sr3Ru2O7 by applying stress

“…Applying uniaxial compressive strain makes the nontilted octahedra in the ground-state structure become tilted by the same amount in all bilayers of the system. This is opposed to the case when a [001] surface is created in the system and octahedra tilts only emerge within the first surface bilayer [2].…”

“…For all calculations we have used a hybrid functional based on a mixing of 10% HFX with 90% PBESol [25] exchange potential (PBES-10). This particular functional has been shown to accurately capture the electronic, magnetic, and structural properties of bulk [3] and surface Sr 3 Ru 2 O 7 [2].…”

“…The most prominent effect at the surface is the octahedral tilt and increased rotation [1]. In our previous study we found that electronic and magnetic properties are not coupled with octahedra rotations but tilting of the octahedra produces a less conducting state at the surface [2]. This result lead us to apply uniaxial compressive strain along the [001] direction to force tilting of the octahedra throughout the structure and found two hidden phases.…”

“…In this work we investigate the application of in-plane uniaxial and biaxial tensile strains on Sr 3 Ru 2 O 7 . The study was motivated by our recent results on applying uniaxial compressive strain along the c-axis where inplane lattice parameters were progressively expanded ul-timately yielding to metal-to-insulator (MIT) and magnetic phase transitions [2]. This lead us to the hypothesis that in-plane tensile strain could produce similar phase transitions but at a lower stress.…”