Reinforced magnetic properties of Ni-doped BiFeO3 ceramic
  Multiferroic materials attract considerable interest because of the wide range of potential applications such as spintronic devices, data storage and sensors. As a strong candidate for the applications among the limited list of single-phase multiferroic materials, BiFeO3 (BFO) is a quite attractive material due to its multiferroic properties at room temperature (RT). However, BFO is widely known to have large leakage current and small spontaneous polarization due to the existence of crystalline defects such as oxygen vacancies. Furthermore, the magnetic moment of pure BFO is very weak owing to its antiferromagnetic nature. In this paper, the effects of Ni2+ substitution on the magnetic properties of bulk BFO have been investigated. BFO, and BiFe0.99Ni0.01O3, BiFe0.98Ni0.02O3 and BiFe0.97Ni0.03O3 (BFNO: Ni-doped BFO) ceramics were prepared by solid-state reaction and rapid sintering, and analyzed by structural and magnetic-property measurements. The leakage current density was measured at RT by using a standard ferroelectric tester. All the Ni-doped BFO exhibit the similar rhombohedral perovskite structure (R3c) to that of BFO. The magnetic properties of Ni-doped BFO are much enhanced with respect to BFO prepared at the same conditions, since the enhanced ferromagnetic interaction is caused by the Fe/Ni coupling. 
J. S. Hwang, Y. J. Yoo, J.-H. Kang, K. H. Lee, B. W. Lee, S. Y. Park   and Y. P. Lee
cond-mat.mtrl-sci physics.chem-ph