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Abstract: The transition-metal (TM) doped BiFeO3 thin films have been deposited on Si (100) substrate by spray pyrolysis technique and their electric, magnetic, ferroelectric and magnetoelectric properties were studied. The leakage current in Mn- and Co-doped BiFeO3 have been found to be about one order magnitude lower than that of BiFeO3 sample. The improvement in magnetization (M s ) and polarization (P r ) have been found in the TM doped BiFeO3 samples and reaching a maximum value of M s ~0.21μ B per formula unit for the Cr-doped and P r ~55.6μC/cm2 for Mn-doped samples. The study of magnetoelectric coupling characteristics gave optimum coupling coefficient at critical value of the magnetic field, which may be due to the suppression of cycloid spin structure. The maximum coupling sensitivity of 10.48V/cmOe was observed for Mn doped samples. [Copyright &y& Elsevier]

Abstract: Magnetoelectric effect has been studied in films of BiFeO3 with particle sizes in the range, 12 to 92nm deposited by spray pyrolysis method. The field emission scanning electron microscopy images show that the films were uniform, dense and of near spherically shaped nano-particles. The ferroelectric loops were studied in the presence of magnetic field and about 30% increase in the remanent polarization was obtained. The enhanced polarization was observed above some critical value of the applied field which is attributed to the suppression of cycloidal spin structure. A large coupling between ferromagnetic and ferroelectric order parameters has been found at room temperature. It has been attributed to the large ferroelastic domains and suppression of the cycloid spin structure. [Copyright &y& Elsevier]

Abstract: The particle size effect in the range 10–150nm on the magnetic properties and phase transitions in BiFeO3 samples prepared by spray pyrolysis method has been studied. The phase purity and structure have been investigated by XRD and FTIR spectroscopy analysis. The FTIR peaks of the nanoparticles shift to lower wave number due to increase surface area and grain boundaries. The Fe-SEM and TEM images show that the particles are uniform, dense and of nearly spherical shape nanoparticles. The significant enhancement in magnetization with finite coercive field has been observed in 12nm particle size samples. The increase in magnetization is about four times larger than that of the bulk samples. It has been attributed to the suppression of the cycloidal spin structure due to large uncompensated spins of Fe+3 ions at the surface of the particle and the adsorbate induced spin polarization screening in BFO nanoparticles. The phase transitions above room temperature have been investigated by DTA measurements and show that Néel temperature (T N) and Curie temperature (T c) increase with particle size. The shift in T N and T c values with particle size are fitted well to the finite scaling models. The microscopic parameters like correction length, characteristic microscopic dimension of the system and critical particle size have been evaluated which provide more physical insight in the finite scaling effect in the nanoparticle samples. [Copyright &y& Elsevier]

Abstract: The ferroelectric properties of BiFeO3 (BFO) films spray deposited on porous silicon have been studied. The analysis of XRD and FESEM investigations show that the crystalline strain in the BFO films increases with pore size. The BFO films on porous silicon substrate showed improvement in ferroelectric fatigue behavior, remanent polarization and ferroelectric switching time. A maximum memory window of 5.54 V at 1 MHz and a large remanent polarization (Pr ) of 13.1 μC/cm2 have been obtained at room temperature. The improvement in the ferroelectric properties of these films has been correlated to the crystalline strain. [Copyright &y& Elsevier]