Effect of Misfit Dislocation in SrIrO₃ heterostructures

Iridates benefit from a large spin-orbit coupling where the Ir-O bond geometry strongly impacts both electronic and magnetic properties leading to topologically non-trivial spin textures. The coupled spin and charge combined with interface engineering provides a unique opportunity to harvest the expected magnetoelectric coupling in BaTiO₃ (BTO)/ SrIrO₃ (SIO) superlattices where induced non-centrosymmetricity is present. A clear picture of the microstructures at interface is required for understanding the intrinsic structure-property relationship. By using scanning/transmission electron microscopy, we studied the structural feature of the BTO/SIO superlattices on SrTiO₃ (001) substrate. Misfit dislocations are found in the superlattices to compensate the large lattice parameter and octahedra rotation mismatch between BTO and SIO. Due to the gradual relaxation of mismatch strain, the density of the misfit dislocation changes as a function of the superlattice thickness, and it almost disappears under a certain thickness. Moreover, the effect of the misfit dislocation on the magnetic property will also be discussed.