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

Highlights: • NiFe₂O₄ was selected as the ferromagnetic material to form FM/BFO heterostructures. • The NFO/BFO bilayer film was prepared via a sol-gel spin-coating technique. • The exchange bias effect of the NFO/BFO interface was studied. • The blocking temperature of NFO/BFO heterojunction was raised to 300 K. • Moreover, a spin-glass-like behavior has been observed in the NFO/BFO bilayer film. 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 H_EB/H_C 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.