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Special Seminar | X-Ray Science

Manipulating Magnetic States in Pseudospin-Half Square-Lattice Iridates

XSD/MM Special Presentation

Abstract: Tuning the interactions between spin, charge, orbital, and lattice degrees of freedom provides a powerful approach to discovering novel emergent states in quantum materials. The interactions between these degrees of freedom can be effectively adjusted through external stimuli, including dimensionality, strain, magnetic and electric fields, and other variables. During this presentation, I will show the new emergent states in thin film and bulk samples of square-lattice iridates induced by manipulating the dimensionality and strain in the system. 

In the first part of my talk, I will focus on the experimental realization of a hybrid SrIrO3/SrTiO3 superlattice that integrates monolayer and bilayer square lattices in one layered structure. Using synchrotron x-ray diffraction, resonant x-ray magnetic scattering, magnetization, and resistivity measurements, we discovered that the hybrid superlattice exhibited unique properties that cannot be explained by simply adding the characteristics of the single-layer and bilayer systems. Interestingly, the entire hybrid superlattice orders simultaneously through a single antiferromagnetic transition at temperatures similar to the bilayer system, but with all the Jeff = 1/2 moments mainly pointing in the ab plane, similar to the single-layer system. 

In the latter part of my talk, I will present our recent work on Sr2IrO4, where we introduced orthogonal anisotropy by applying uniaxial strain along the <110> axes to compete with spontaneous anisotropy. This led to the emergence of elasto-incommensurate magnetic order of multiple-q spin modulations near the antiferromagnetic temperature of 223 K. The resonant x-ray magnetic scattering measurements showed that the moments were waving around the strain direction.