Emergent interlayer magnetic order via strain-induced orthorhombic distortion in the 5d Mott insulator Sr2IrO4

TL;DR

This study demonstrates that strain-induced orthorhombic distortion in Sr2IrO4 films induces a La2CuO4-like interlayer antiferromagnetic order, revealing strain as a tool to control magnetic phases in 5d Mott insulators.

Contribution

The paper shows that biaxial strain causes a transition from tetragonal to orthorhombic symmetry, leading to a new interlayer magnetic order in Sr2IrO4, which was not previously observed.

Findings

Orthorhombic distortion exceeds 1.5% in Sr2IrO4 films.

Interlayer antiferromagnetic order similar to La2CuO4 observed.

Strain controls the competition between interlayer exchange and pseudo-dipolar interactions.

Abstract

We report a La2CuO4-like interlayer antiferromagnetic order in Sr2IrO4 films with large orthorhombic distortion (> 1.5%). The biaxial lattice strain in epitaxial heterostructures of Sr2IrO4/Ca3Ru2O7 lowers the crystal symmetry of Sr2IrO4 from tetragonal (C4) to orthorhombic (C2), guiding the Ir 5d Jeff = 1/2 pseudospin moment parallel to the elongated b-axis via magnetic anisotropy. From resonant X-ray scattering experiments, we observed an antiferromagnetic order in the orthorhombic Sr2IrO4 film whose interlayer stacking pattern is inverted from that of the tetragonal Sr2IrO4 crystal. This interlayer stacking is similar to that of the orthorhombic La2CuO4, implying that the asymmetric interlayer exchange interaction along a and b-directions exceeds the anisotropic interlayer pseudo-dipolar interaction. Our result suggests that strain-induced distortion can provide a delicate knob for tuning the long-range magnetic order in quasi-two-dimensional systems by evoking the competition between the interlayer exchange coupling and the pseudo-dipolar interaction.