Synopsis

Controlling Magnetism by Electricity

Physics 7, s150
Small voltages can control the magnetic properties of thin films at room temperature.
C. Bi et al., Phys. Rev. Lett. (2014)

Modern hard drives store information by controlling the magnetization of their memory elements with magnetic fields. Such devices might become more energy efficient if the magnetization could be controlled by electric fields, but many materials so far investigated only function at very low temperatures. Now, researchers in Weigang Wang’s group at the University of Arizona, Tucson, and collaborators have shown that electric fields can efficiently control the magnetic properties of a thin cobalt film at room temperature. Their results reveal that small applied voltages can change the magnetic state of the material in a nonvolatile way—a crucial feature for memory devices.

Previous research showed that electric fields could switch the magnetization of thin ferromagnetic films, but the effect was always small and disappeared as soon as the field was turned off since it depended on electric field-induced charge rearrangements. Now, the authors have achieved a large, nonvolatile effect by inducing oxygen ions to migrate through an oxide layer and change the oxidation state of the cobalt thin film. The researchers sandwiched a few-atom-thick cobalt film between a metallic and an oxide layer and characterized the magnetic anisotropy of the cobalt film as a function of the polarity and duration of an electric field applied to the film. Voltages as low as a few volts resulted in a reversible and nonvolatile anisotropy change that was over two orders of magnitude larger than in previous studies. The effect caused changes in the sample’s transverse electrical resistance that could be used in electrically driven devices reminiscent of spin valves, although the speed of its buildup (tens of seconds) remains an obstacle for practical applications.

This research is published in Physical Review Letters.

–Katherine Kornei


Subject Areas

MagnetismSpintronics

Related Articles

Spin Polarization Without Net Magnetization
Spintronics

Spin Polarization Without Net Magnetization

An analysis of magnetic symmetry groups in antiferromagnets points to a new class of materials that will be useful for spintronics.  Read More »

Cooling a Spin Relaxation Hot Spot
Magnetism

Cooling a Spin Relaxation Hot Spot

The rate at which electron spins relax in silicon quantum dots is controlled by the strength and direction of external magnetic fields. Read More »

Spin Current in an Antiferromagnet is Coherent
Condensed Matter Physics

Spin Current in an Antiferromagnet is Coherent

Experiments show that a spin current moves as a coherent evanescent spin wave through an antiferromagnet layer sandwiched between two ferromagnets. Read More »

More Articles