In this investigation, Gd and Mn co-doped Bi 0.85 Gd 0.15 Fe 1-x Mn x O 3 (x=0.0-0.15) nanoparticles have been prepared to report the influence of co-substitution on their structural, optical, magnetic and electrical properties. Due to simultaneous substitution of Gd and Mn in BiFeO 3 , the crystal structure has been modified from rhombohedral (R3c) to orthorhombic (Pn2 1 a) and the Fe-O-Fe bond angle and Fe-O bond length have been changed. For Mn doping up to 10% in Bi 0.85 Gd 0.15 Fe 1-x Mn x O 3 nanoparticles, the saturation magnetization (M s ) has been enhanced significantly, however, for a further increase of doping up to 15 %, the M s has started to reduce again. The co-substitution of Gd and Mn in BiFeO 3 nanoparticles also demonstrates a strong reduction in the optical band gap energy and electrical resistivity compared to that of undoped BiFeO 3 .

In the modern micro-electronics, transition metal oxides due to their colossal values of dielectric permittivity possess huge potential for the development of capacitive energy storage devices. In the present work, the dielectric permittivity and the effects of temperature and frequency on the electrical transport properties of polycrystalline NdFeO3, prepared by solid state reaction method, are discussed. Room temperature Mossbauer spectrum confirms the phase purity, octahedral environment for Fe ion, and high spin state of Fe3+ ion. From the impedance spectroscopic measurements, three relaxation processes are observed, which are related to grains, grain boundaries (gbs), and electrode-semiconductor contact in the measured temperature and frequency ranges. Decrease in resistances and relaxation times of the grains and grain boundaries with temperature confirms the involvement of thermally activated conduction mechanisms. Same type of charge carriers (i.e., small polaron hole hopping) have been found responsible for conduction and relaxation processes through the grain and grain boundaries. The huge value of the dielectric constant (∼8 × 103) at high temperature and low frequency is correlated to the Maxwell-Wagner relaxation due to electrode-sample contact.

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We report on the magnetic and transport measurements in an Fe-doped colossal magnetoresistance compound (La 0.65 Ca 0.35 MnO 3 ). Increased spin disorder and a decrease of T c with increasing Fe content are evident. We find that the resistivity data above T p fits better to a variable range hopping model and the localization length decreases with Fe content. The variations in the critical temperature T c , confinement length, magnetic moment and magnetoresistance show a rapid change at about 4-5% Fe. The maximum magnetoresistance is seen to increase consistently with the addition of Fe and increases up to 400% for 8% Fe. The effect of Fe is seen to be consistent with the disruption of the Mn-Mn exchange, possibly due to the formation of magnetic clusters.

Mechanism behind the high thermoelectric power factor of SrTiO3 by calculating the transport coefficients J. Appl. Phys. 113, 053705 (2013); 10.1063/1.4788809Generation-dependent charge carrier transport in Cu(In,Ga)Se2/CdS/ZnO thin-film solar-cells Electrical transport properties of electrospun cadmium titanate (CdTiO 3 ) fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000 • C yielded the single phase perovskite fibers having diameter ∼600 nm -800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K -420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC) with traps at higher voltages at all temperatures (200 K -420 K). Trap density in our fibers system is N t = 6.27 × 10 17 /cm 3 . Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH) from 200 K -300 K. The localized density of states were found to be N(E F ) = 5.51 × 10 21 eV −1 cm −3 at 2 V. Other VRH parameters such as hopping distance (R hop ) and hopping energy (W hop ) were also calculated. In the high temperature range of 320 K -420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV.

Polycrystalline ceramics, Bi1-2xBa2xFe1-xNbxO3 (x = 0.00–0.15), were synthesized by solid state reactions method. X-ray diffraction data have revealed elimination of impurity phases and an increase in unit cell volume with Ba and Nb substitution. Diffraction peak splitting is found to be suppressed which indicates a decrease in octahedral distortion. The Mössbauer spectra demonstrate the suppression of spiral spin modulation of the magnetic moments resulting in enhanced ferromagnetism with increasing dopant concentration. The leakage current density of the sample with x = 0.10 is found to be greatly reduced up to six orders of magnitude as compared to the undoped sample. Ohmic conduction is found to be dominant mechanism in all the samples, however, undoped sample showed space charge limited conduction in high electric filed region, while the sample with x = 0.15 exhibited grain boundary limited conduction in low electric field region.

Improvement in magnetic and electrical properties of multiferroic BiFeO3 in conjunction with their dependence on particle size is crucial due to its potential applications in multifunctional miniaturized devices. In this investigation, we report a study on particle size dependent structural, magnetic and electrical properties of sol-gel derived Bi0.9Ba0.1FeO3 nanoparticles of different sizes ranging from ∼ 12 to 49 nm. The substitution of Bi by Ba significantly suppresses oxygen vacancies, reduces leakage current density and Fe 2+ state. An improvement in both magnetic and electrical properties is observed for 10 % Ba-doped BiFeO3 nanoparticles compared to its undoped counterpart. The saturation magnetization of Bi0.9Ba0.1FeO3 nanoparticles increase with reducing particle size in contrast with a decreasing trend of ferroelectric polarization. Moreover, a first order metamagnetic transition is noticed for ∼ 49 nm Bi0.9Ba0.1FeO3 nanoparticles which disappeared with decreasing particle size. The observed strong size dependent multiferroic properties are attributed to the complex interaction between vacancy induced crystallographic defects, multiple valence states of Fe, uncompensated surface spins, crystallographic distortion and suppression of spiral spin cycloid of BiFeO3.