Oxide interfaces

Using heteroepitaxial thin films, we have discovered that it is possible to nanoengineer entirely new strain states into thin films. This opens up a route to creating new properties in strongly correlated oxides where properties are very closely linked to structure. We have several examples showing strongly enhanced and/or ‘different’ properties in oxides.

Ferroelectrics for Microenergy Harvesting

We have created green ferroelectrics with strongly enhanced polarisation and very high temperature operation (few hundred ^oC operation). There is great potential for applications in microenergy harvesting. Furthermore the sign of the transverse piezoelectric coefficient, d₃₁, exceeds Pb(Zr_1-xTi_x)O₃ (PZT) films, with a value > 200 pm V^-1_.

a) Microactuator structure made from nanocomposite ‘green ferroelectric’.b) Vertical deflection of composite actuator compared to ‘standard’ PZT one (note the opposite direction of the deflection).  c) d₃₁ at a specific temperature normalized to the room temperature value.

Adv. Func. Mater. 23 (47) 5881 (2013) DOI:10.1002/adfm.201300899

Inducing Magnetism at Oxide Interfaces

Understanding interface magnetism in complex metal-oxide heterostructures is both scientifically and technologically important.  Using polarised neutron reflectometry, we observed magnetisation throughout the thickness of La_0.7Sr_0.3MnO₃/BiFeO₃ (LSMO/BFO) superlattices. For example, a magnetisation of ~75 ± 25 kA/m, which was in consistent with the value of macroscopic magnetisation measured by SQUID magnetometer, was observed in the BFO layer at 10 K. The enhanced magnetic state at the interface is explained by the density functional theory, where the size of band gap of BFO plays an important role in determining the induced magnetisation.

Phys. Rev. Lett. 113, 047204 DOI: 10.1103/PhysRevLett.113.047204

Part of research conducted in the Driscoll Group