Giant Domain Walls and Intrinsic Heterogeneity in 214 Cuprate Superconductors

Structural phase transitions generate complex microstructures that often govern material functionality, yet directly resolving their three-dimensional organization in bulk samples remains challenging. Here we employ scanning three-dimensional x-ray diffraction (3DXRD) to resolve the bulk microstructure of La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}, a prototypical 1/8-doped cuprate in which structural and electronic heterogeneity is well established. We reveal remarkably broad tetragonallike domain wall regions within the nominally orthorhombic crystal structure, and, upon cooling to 100 K, a fine microstructure of orthorhombiclike stripes embedded within the tetragonal matrix that has significant consequences for interpreting the interplay between structural and electronic heterogeneity in this class of materials. More broadly, this work establishes 3DXRD as a powerful approach for resolving bulk microstructures and understanding their role in emergent functionality.