Stretched film reshapes magnetic pattern express
A thin film of iron oxide SrFeO3 sits on a substrate that slightly stretches it. Inside the film, the magnetic moments of atoms twist into a spiral, like a spiral staircase. The strain changed that staircase: the step became shorter, and the axis itself tilted.
The reason lies in oxygen. A stretched lattice more readily loses oxygen atoms, leaving vacancies. These vacancies push neighboring iron atoms apart, and the iron–oxygen bonding changes. One type of magnetic exchange (direct, through oxygen) strengthens, while another (via itinerant electrons) weakens. As a result, the spiral compresses and tilts.
This trick, controlling magnetism through chemical expansion, opens a route to tuning magnetic patterns without strong magnetic fields. In the future, it could benefit devices where information is carried not by electrons but by magnetic vortices.
The iron oxide SrFeO3 belongs to a family of materials where oxygen easily leaves the lattice, like water from a sponge. Each departing oxygen molecule leaves behind a vacancy that slightly pushes neighboring atoms apart.
In Peter Watts's novel Blindsight, alien ships use magnetic fields for camouflage. Controlling magnetic vortices in films is a step toward such exotic technology.