A piece of zinc oxide film lies on a table. A magnet is brought near, and slowly rotated around the film. The film, thinner than a human hair, begins to change its dimensions: now contracting, now stretching. This property is called magnetostriction — the ability of a material to deform under a magnetic field.

Indian scientists measured this effect using a homemade optical device — a cantilever magnetometer. A light beam reflects off the film mounted on a thin cantilever, and the slightest bending of the cantilever is detected by the shift of the beam. It turned out that as the magnetic field rotates from 0 to 90 degrees, the film behaves differently: at some angles it only stretches, at others only contracts, and at some it first does one, then the other. This switching is related to the internal crystal structure of zinc oxide.

The practical benefit is clear: such a film could be used to make tiny sensors that respond to the direction of a magnetic field, or microactuators controlled by rotating a magnet. All of this is useful in micro- and nanoelectronics, where compactness and precision matter.