Enhancement of multiferroic properties of nanocrystalline BiFeO₃ powder by Gd-doping

Large leakage current and a very low magnetic moment are the two most disadvantages of BiFeO₃ (BFO), which hinder the possibilities of its application in modern devices. An enhancement of the multiferroic properties of BFO is a real challenge to the scientific community. We are able to achieve improve magnetic, electric and magneto-dielectric (MD) properties of sol-gel prepared nanocrystalline BFO by virtue of the beneficial effect of gadolinium doping. The phase-purity and nanocrystalline nature of the samples have been confirmed by the X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Both dc and ac electrical properties were measured to understand the detail charge transport mechanism. The dc electrical resistivity was found to arise due to a variable range hopping conduction mechanism. The variation of ac-conductivity, as a function of frequency in the range (20 Hz-1 MHz) and temperature (298-523 K), was explained on the basis of the correlated barrier hoping (CBH) conduction mechanism. The origin of the improved magnetic and electrical properties have been attributed to a possible suppression of the inhomogeneous magnetic spin structure and/or broken periodicity of the spin cycloid of BFO due to smaller crystallite size, and a decrease of the oxygen vacancies. Our findings demonstrate the fundamental importance of doping in enhancing the multiferroic properties, which would open up the possibility of using BFO in designing spintronic devices.