Spin-lattice coupling in multiferroic Pb(Fe1/2Nb1/2)O3 thin films

We made magnetization and x-ray diffraction measurements on an epitaxial Pb(Fe1/2Nb1/2)O3 200 nm film. From the temperature dependence of the out-of-plane lattice parameter, we can assign a Burns’ temperature at Td∼640 K, a temperature at T∗∼510 K (related to the appearance of static polar nanoregions), and an anomaly occurring at 200 K. The latter is precisely the Neel temperature TN determined from magnetization and points to spin-lattice coupling at TN∼200 K. We also observe “weak ferromagnetism” up to 300 K and propose superantiferromagnetic clusters as a plausible scenario to explain this hysteresis above TN.