Chemists control perovskite structure to unlock magnetisation and polarisation at once
Breakthrough has potential applications in information storage and processing
Crystalline materials that combine electrical polarisation and magnetisation could be advantageous in applications such as information storage, but these properties are usually considered to have incompatible chemical bonding and electronic requirements.
Now, scientists at the University of Liverpool, UK, working on perovskite (CaySr1-y)1.15Tb1.85Fe2O7, have controlled the structure of the material to simultaneously generate both magnetisation and electrical polarisation above room temperature.
The two resulting properties are magnetoelectrically coupled as they arise from the same displacements, an advance which has potential applications in information storage and processing, say the researchers who published the results in Science last week.
For information storage, these materials can combine low-power electrical writing of information with non-destructive magnetic reading, while logic devices using them for information processing can work without charge current flow. The increasing energy consumption of computers and internet-enabled devices could be a significant future sustainability challenge.
Liverpool Materials Chemist, Professor Matthew Rosseinsky, said: "We were able to demonstrate that the magnetisation and polarisation are coupled by measuring the linear magnetoelectric coefficient, a key physical quantity for the integration of such materials in a device. This coupling arises because both properties are produced by the same single set atomic motions that we built in to the material."
"There are a number of challenges still to address, particularly switching the polarisation and making the material more electrically insulating, before applications of this material for information storage can be considered."
"By designing-in the required atomic-level changes using both computation and experiment together, we produced three properties (polarisation, magnetisation, magnetoelectricity) from a material that initially displayed none of them.
"Design of materials properties at the atomic scale is difficult, as it is quite a different problem from designing a large-scale object like a bridge or a car, but would be very desirable across the whole spectrum of properties. We are currently working on materials design in other areas, such as batteries or solar energy harvesting, where improvements are also needed."
'Tilt engineering of spontaneous polarization and magnetization above 300 K in a bulk layered perovskite', by Michael J.Pitcher et al, Science 23 January 2015: Vol. 347 no. 6220; DOI: 10.1126/science.1262118
