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

Exchange bias properties in bismuth ferrite nanostructures produced by pulsed laser deposition with different mophologies are reported. Distinct bismuth ferrite nanostructures were obtained, driven by the background pressure in the deposition chamber: vacuum (10
⁻⁶
Torr) and high pressures (0.25 and 4.0 Torr) of O
2
and submitting them to a thermal treatment after deposition at 500°C. The bismuth ferrites nanostructures range from very compact thin-film (10
⁻⁶
Torr), to clustered nanoparticles (0.25 Torr), to an arregement of nanoparticles contacting with fewer neighbours (4.0 Torr). The field-cooled magnetization curves of the nanostructures display a horizontal shift (exchange bias), and for clustered nanoparticles, the exchange bias coexists with a vertical shift. The magnetic properties are discussed considering the morphologies of the nanostructures and their role in the magnetic anisotropy and interaction between nanoparticles.