Exchange bias in spin-glass-like NiFe2O4/BiFeO3 heterojunction at room temperature

In order to improve blocking tepmerature of the exchange bias effects in heterojunction composing of ferromagnetic (FM) materials and multiferroic BiFeO3 (BFO). NiFe2O4 (NFO) was selected as the FM material to form FM/BFO heterojunction for its high Curie temperature in this paper. NFO/BFO bilayer film was prepared on Pt/Ti/SiO2/Si substrate via a simple sol-gel spin-coating technique. Exchange bias field at room temperature has been observed as expected and HEB/HC was 4.5%. The M-T curves of the NFO/BFO heterostructure indicated that the magnetic anisotropy disappeared above 300 K. Furthermore, a field-dependent irreversible magnetization behavior and an exponential decay of coercive field and exchange bias field with temperature were found, which suggested a spin-glass-like state existed in the NFO/BFO heterostructure.