Ferroelectricity and Ferromagnetism of M-Type Lead Hexaferrite

Polarization and related properties in the M-type lead hexaferrite (PbFe12O19) are reported for the first time. The remnant polarization of PbFe12O19 exhibits a maximum value of 104C/cm(2), as well as large spontaneous polarization at room temperature. Annealing of PbFe12O19 in oxygen plays a key role in the saturation of its polarization hysteresis loop because it greatly enhances the ceramic's electric resistance. Two current peaks in the I-V curve reveal a polarization switch, providing effective evidence for the ferroelectricity of PbFe12O19. Its temperature-dependent dielectric constant undergoes colossal change in the vicinity of two temperatures (322 degrees C and 518 degrees C), which are assigned to the transitions from ferro- to antiferro- and antiferro- to paraelectric phases, respectively. The plots of logarithm of (1/epsilon-1/epsilon(m)) as a function of logarithm of (T-T-m) obey a modified Curie-Weiss law, verifying the relaxor ferroelectric characterization of PbFe12O19. The ceramic also exhibits a strong magnetic hysteresis loop. These combined functional responses of ferroelectricity and ferromagnetism in PbFe12O19 ceramic present an opportunity to create electric devices that actively couple the magnetic and ferroelectric orders.