Multiferroic Behaviour in A- and B-site Cation Ordered Perovskites

Ferroelectric (FE) oxides are an important class of materials with widespread application in many global markets including consumer electronics, piezoelectric sensors and actuators. These materials exhibit an electric dipole which can be spontaneously aligned on application of an electric field. The direction of this dipole can then be switched by alternating the electric field and exploited as on/off or binary 0/1 states. Currently PbZrxTi1-xO3 (PZT) is the most widely exploited FE material. However, the use of lead in commercial products is not favourable meaning we need to find a lead free replacement. Ferromagnetic materials can be seen to be analogous to FE materials in that these materials exhibit a magnetic spin which can be aligned on the application of a magnetic field and exploited in a similar way. More recently, the coupling of ferromagnetism (FM) or antiferromagnetism (AFM) and ferroelectricity has emerged as an area of great technological potential. Coupling in these materials would allow for the switching of the FE state with a magnetic field and vice versa. These so called multiferroic materials could lead to whole host of next generation devices with improved performances over either their ferroelectric or magnetic counterparts.

The synthesis of multiferroic materials however, proves challenging since ferroelectricity typically requires no unpaired electrons whilst magnetism requires unpaired electrons: the two order parameters tend to be mutually exclusive. One methodology to overcome these limitations is to order magnetic and ferroelectric ions onto different sites within the crystal lattice. Doubly ordered perovskites (AA'BB'O6) can exhibit ordering of both the A-site and B-site cations simultaneously. Clearly this offers a potential route to new multiferroic materials but to date this has received little attention within the literature. This proposal therefore seeks to investigate doubly ordered perovskites with the aim of designing new multiferroic materials with the potential for application.

The work described in this proposal primarily represents primarily fundamental science contributing new materials and understanding to the field of multiferroics with little commercial and thus societal impact in the short term. However, the technological importance of multiferroic materials cannot be understated with multiferroics expected to find application in next generation sensor, actuator, transducers and memory devices operating with improved performances over the currently used ferroelectric or magnetic counterparts. It is therefore a distinct possibility that the novel materials developed as part of this proposal will potentially be developed for device application in the long term. In order to ensure that the full impact of this proposal is achieved the PI will undertake the following impact activities

Academic dissemination: The primary beneficiaries of this work will be other academics within the ferroelectrics and multiferroics fields as well as those in broader materials research. The PI will continue to disseminate through traditional routes, such as publication in high impact journals and conference participation. In addition the PI will seek ways to ensure the work conducted as part of this proposal reaches as wider audience as possible through for example participation and general materials interest conferences as well as more focussed multiferroic specific symposia.

Teaching and Outreach: Outreach is an important tool to bring scientific excellence to wider audiences and should not be excluded as potential impact. The University of Kent has a dedicated outreach officer who works with local schools and the PI will work together with her to investigate ways of disseminating the results generated here.

Commercial and societal impact: The technological importance of these materials cannot be understated and it is therefore important to recognise potential long term beneficiaries of the research proposed here. The PI has already identified several routes through which to start dialogue with potential commercial industries (please see pathways to impact). In addition if materials generated in this proposal are to be exploited for device applications they will be required as thin films. The PI already has established collaborations with groups focussed on thin films and links to the thin film communities and will ensure promising candidate materials reach their full potential.