Spin-glass behavior of nanocrystalline multiferroic bismuth ferrite lead titanate

Multiferroic bismuth ferrite lead titanate exhibiting both ferroelectricity and ferromagnetism in a single perovskite phase has been chemically synthesized in the form of nanocrystalline films with large surface/interface to volume atomic ratio. The films show both electric polarization and magnetization hysteresis loops and demonstrate behavior consistent with the existence of a spin-glass state at temperatures well above the room temperature. Anomalous magnetic properties and glassy dynamics are associated with a high degree of magnetic frustration and disorder due to the spatial confinement in nanosized crystalline grains, random distribution of anisotropy axes in the grains, inter-grain interaction and the effects of uncompensated spins on the large effective surface and interface favored by the nanocrystalline morphology of the films.