Ti-doped BiFeO3 ceramics prepared by a mixed-oxide route were structurally characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), giving evidence of the formation of an inner structure at the nanometric scale. The observed nanograins are separated by Ti-rich areas that originate due to the tendency of the titanium dopant to segregate from the perovskite lattice. Such a peculiar nanostructure is responsible for the changes produced in both the electrical and the magnetic properties of BiFeO3 upon titanium doping: the Ti-rich interfaces act as resistive layers that increase the direct-current (dc) resistivity of the material, while the existence of structural domains in the scale of tens of nanometers causes a ferrimagnetic-like behavior with a huge coercive field (on the order of 20 kOe), even at room temperature.

This work has been conducted within the CICYT MAT 2010-16614, CSD2009-00013, and MAT-27470-C02-02 projects. M.S.B. also acknowledges the Spanish Ministry of Education for the financial support (FPU Program, No. AP2008-00053). T.J. acknowledges the JAE-Doc contract of the Spanish National Research Council (CSIC) and European Science Foundation (ESF). M.P. also acknowledges the Ramón y Cajal Program of MINECO for the financial support.

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