Crystal direction selection by ferroelastic writing

Crystals often have complex structural domains, lacking a general method to remove or deterministically control such local heterogeneity. The resulting heterogeneity in crystal orientations obscures our understanding of material properties and could reduce the reliability and performance of related applications. Here, using mechanical stress from an atomic force microscope tip, we demonstrate ferroelastic writing for deterministic and reversible control of local crystal orientations. By applying this to various oxide thin films, we realize twin-free single crystals and design specific crystal-orientation domain textures at the nanoscale. Furthermore, through magnetoelastic coupling, this approach could mechanically write and erase functional nanoscale magnetic textures unattainable by conventional methods. Thus, pure mechanical force emerges as a versatile means to control structural heterogeneity on demand and to program electronic and spintronic functionalities.