  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.
