High-resolution structure studies and magnetoelectric coupling of relaxor multiferroic Pb(F e0.5 N b0.5) O3

Pb(Fe0.5Nb0.5)O3 (PFN), one of the few relaxor multiferroic systems, has a G-type antiferromagnetic transition at TN=143K and a ferroelectric transition at TC=385K. By using high-resolution neutron-diffraction experiments and a total scattering technique, we paint a comprehensive picture of the long- and short-range structures of PFN: (i) a clear sign of short-range structural correlation above TC, (ii) no sign of the negative thermal expansion behavior reported in a previous study, and (iii) clearest evidence thus far of magnetoelectric coupling below TN. We conclude that at the heart of the unusual relaxor multiferroic behavior lies the disorder between Fe3+ and Nb5+ atoms. We argue that this disorder gives rise to short-range structural correlations arising from O disorder in addition to Pb displacement.