Topochemical Cation Exchange Reactions of Layered Perovskite Oxides

Magnetoelectric materials exhibit coupled ferromagnetic and ferroelectric behaviour and are predicted to have a broad range of applications in electronic data storage and manipulation. We have adopted a strategy of using low-temperature cation-exchange reactions to substitute paramagnetic ions into hybrid-improper ferroelectric phases as a route towards magnetoelectric materials. Following this approach we have prepared FeCaTa2O7, CoCaTa2O7 and ZnCaTa2O7. We propose to collect neutron powder diffraction data from these phases at room temperature to establish their crystal structures, and then on cooling (FeCaTa2O7, and CoCaTa2O7 only) to establish their magnetic structures and to see if the onset of magnetic order induces the phases to adopt polar crystal structures. These data will be compared to previous data collected on WISH from the related phases, MnSrTa2O7 - which is polar and exhibits magnetoelectric coupling, and MnCaTa2O7 - which is polar but does not exhibit magnetoelectric coupling.