Investigation of exchange bias in 0.1MFe2O4/0.9BiFeO3 (M=Co, Cu, Ni) nanocomposite

The 0.1MFe₂O₄/0.9BiFeO₃ (M=Co, Cu, Ni) nanocomposite samples were synthesized by the sol-gel method. Phase composition analysis was carried out, which showed that these bulk samples were composed of a ferrimagnetic MFe₂O₄ (M=Co, Cu, Ni) and a ferroelectric antiferromagnet (FEAF) BiFeO₃ phases, respectively. The magnetic properties of all the samples were investigated by measuring their magnetization as a function of temperature and magnetic field. These results indicated that the magnetic hysteresis loops of 0.1CuFe₂O₄/0.9BiFeO₃ sample sintered in air atmosphere at 550 °C for 3 h exhibited a negative shift and an enhanced coercivity at low temperature ascribed to strong exchange coupling between the BiFeO₃ and CuFe₂O₄ grains. However, there were no magnetic hysteresis loops in both the 0.1CoFe₂O₄/0.9BiFeO₃ sample and the 0.1NiFe₂O₄/0.9BiFeO₃ sample. In view of these results, we tend to think the CuFe₂O₄/BiFeO₃ nanocomposite system may be a useful multifunctional material.