Exchange Bias Effects in Bismuth Ferrite Nanostructures Produced by Pulsed Laser Deposition

The exchange bias characteristics of bismuth ferrite nanostructures with different morphologies produced by pulsed laser deposition (PLD) are reported. Distinct bismuth ferrite nanostructures were achieved by employing different background pressures during deposition: vacuum ( 10^{-6} torr) and high O2 pressures (0.25 and 4.0 torr), as well as thermal treatment after deposition at 500~^{\circ } C. Scanning electron micrographs revealed nanostructures with distinct morphologies, including a highly compact thin film, dense nanoparticle clusters, and arrangement of nanoparticles in contact with fewer neighbors. The field-cooled magnetization curves of the nanostructures display a horizontal shift (exchange bias) across all morphologies studied, along with a vertical shift for dense nanoparticle clusters. The magnetic properties are discussed considering the morphologies of the nanostructures as well as their role in the magnetic anisotropy and interaction between nanoparticles.