Many solid materials have a crystal structure, with atoms that exist in a particular, organized arrangement. The degree of organization can vary among crystals, however. Most crystalline solids are made up of distinct grains, like grains of salt; although not always visible to the naked eye, the boundaries between grains interrupt the lattice structure. A single crystalline structure is one in which the crystal lattice is continuous and uniform throughout the material.

High-quality crystalline materials are the foundation of many familiar devices, such as integrated circuits and solar cells, which use silicon crystals.  A better understanding of these materials, and how to produce high-quality crystalline structures, is important for developing new technologies. Many of these applications require single crystalline ordering, which is challenging to achieve because of their complex and highly organized structure.

Sr₂CrReO₆ is a magnetic oxide ordered in rock-salt structure, with each Cr/Re atom inside an oxygen octahedron. Because the spin of its electrons can be manipulated by magnets at room temperature, it can be used to create spin-based memory devices. This demands nearly perfect crystal ordering of all the atoms, which we achieved using a novel sputtering method in an ultrahigh vacuum.