Nanoscale ordering and multiferroic behavior in Pb(Fe1/2Ta1/2)O-3

We report on structural, microstructural, dielectric, electrical, magnetic, and spectroscopic (Raman and terahertz) properties of lead iron tantalate Pb(Fe1/2Ta1/2)O-3 ceramics. Raman spectroscopy revealed the presence of nanoscale ordering though it is forbidden in bulk by crystal symmetry. The dielectric properties of Pb(Fe1/2Ta1/2)O-3 show a typical relaxor ferroelectric behavior with long-range disorder while the magneto-electric properties show an interesting multiferroic behavior (coexistence of ferroelectric and magnetic order) in the same phase. The temperature variation in field cooled magnetization shows anomalies at about 55(+/- 5) and 180(+/- 5) K indicating the existence of two Neel temperatures in agreement with theoretical predictions. The zero-field-cooled magnetization as a function temperature and field reveals the existence of spin-glasslike behavior at low temperature like single crystal. The electrical conduction behavior satisfies the modified Schottky equation of Simmons at all fields. The ac conductivity as a function of frequency shows an excellent fit to the universal power law. Terahertz spectroscopy shows an opaque nature of Pb(Fe1/2Ta1/2)O-3 in midin-frared and far-infrared wavelengths.