Voltage-Controlled Magnetism

Abstract

Physics Many components of modern devices are based on magnetic effects; magnetic read heads, for example, use the phenomenon known as exchange bias, in which two materials that order magnetically are interfaced, causing the magnetic properties of the ferromagnetic layer (in which spins align parallel to each other) to be affected by the antiferromagnetic layer (in which neighboring spins prefer to be antiparallel). In devices, the control of magnetic effects with electric fields is desirable. Building on earlier work that showed a change in the size of the exchange bias effect, Wu et al. demonstrate a reversible switching of the sign of the exchange bias after the application of a voltage pulse. Key to this result is the use of a multiferroic material for the antiferromagnetic layer, in which switching the sign of the voltage pulse causes spins to reverse their direction and changes the distance between the magnetic ions in the antiferromagnetic and ferromagnetic layers; this, in turn, causes the exchange bias to switch. The switching is achieved at constant temperature (without cooling or heating cycles) and without applying additional magnetic fields; the mechanism the authors offer as an explanation may aid in the understanding of the exchange bias effect. Phys. Rev. Lett. 110 , 067202 (2013).