Research paper of the month
May 2013 - Non-volatile electrically driven repeatable magnetization reversal with no applied magnetic field
The key goal in the field of magnetoelectrics is to reverse the magnetization of a magnet using a voltage rather than a magnetic field. This has previously been demonstrated with the assistance of a magnetic field that (self-defeatingly) had to be reversed for each magnetization reversal. This paper demonstrates and explains how to electrically reverse magnetization with no applied magnetic field. The magnetization stays reversed after removing the voltage, and the process is repeatable.
The experimental demonstration was performed using a commercially available multilayer capacitor that was polished to expose some of the interdigitated nickel electrodes. Magnetic force microscopy revealed that one of the electrodes possessed a micron-scale magnetic feature whose magnetization could be repeatably reversed on applying and removing a voltage on the capacitor terminals. The magnetic force microscopy data were found to be quantitatively consistent with a full magnetization reversal, but a full reversal is unlikely in terms of symmetry, so we modelled a slighly less perfect scenario in which the magnetization switches by just under 180°. We argued that the magnetic switching is driven by a fast change of piezoelectric strain from the barium titanate layers between the electrodes.
The figure shows a plausible trajectory for the magnetization of the feature during the electrically driven strain-mediated switching process.
The experiments demonstrate that it is possible to achieve non-volatile electrically driven repeatable magnetization reversal with no applied magnetic field, and the model should inspire the design of data-storage devices that adopt electric-write magnetic read protocols.
M. Ghidini, R. Pellicelli, J. L. Prieto, X. Moya, J. Soussi, J. Briscoe, S. Dunn and N. D. Mathur, Nature Communications 4 (2013) 1453