We describe systematic studies on Nd and Mn co-doped BiFeO₃, i.e., (Bi_0.95Nd_0.05)(Fe_0.97Mn_0.03)O₃ (BNFM) polycrystalline electroceramics. Raman spectra and X-ray diffraction patterns revealed the formation of rhombohedral crystal structure at room temperature, and ruled out structural changes in BiFeO₃ (BFO) after low percentage chemical substitution. Strong dielectric dispersion and a sharp anomaly around 620 K observed near the Néel temperature ($T_N$ ∼ 643 K of BFO) support strong magneto-dielectric coupling, verified by the exothermic peak in differential thermal data. Impedance spectroscopy disclosed the appearance of grain boundary contributions in the dielectric data in the region, and their disappearance just near the Néel temperature suggests magnetically active grain boundaries. The resistive grain boundary components of the BNFM are mainly responsible for magneto-dielectric coupling. Capacitive grain boundaries are not observed in the modulus spectra and the dielectric behavior deviates from the ideal Debye-type. The ac conduction studies illustrate short-range order with ionic translations assisted by both large and small polaron hopping. Magnetic studies indicate that the weak antiferromagnetic phase of BNFM ceramics is dominated by a strong paramagnetic response (unsaturated magnetization even at applied magnetic field of 7 T). The bulk BNFM sample shows a good in-plane magnetoelectric coupling (ME) coefficient.

Delafossite p-type ${\text{CuFeO}}_2$ (CFO) semiconductors were synthesized by a modified solid state reaction technique and investigated by x-ray diffraction, x-ray photoemission spectroscopy (XPS), energy dispersive x-ray spectroscopy, and scanning electron microscopy, revealing the single-phase nature of CFO with 1:1 Cu/Fe atomic ratio. The valance states of CFO were examined by XPS and suggest Cu and Fe ions are in $+1$ and $+3$ valance states with high spin $\text{S}=5/2$ . The “turn-on field” which is the macroscopic field needed to get an emission current of 9 nA, was calculated as $5.72\text{V}/\mu \text{m}$ . Room temperature Raman spectra of CFO displayed two main Raman active modes at ${\text{E}}_{\text{g}}\sim 351{\text{cm}}^{-1}$ and ${\text{A}}_{\text{g}}\sim 692{\text{cm}}^{-1}$ in accord with other delafossite structures. Temperature dependent Raman spectra showed that both the modes shifted to lower frequency with significant decrease in intensity with increase in temperature. Frequency shift and linewidth of both phonon lines matched well with the theoretical damped harmonic oscillator model based on thermal expansion of the lattice and their anharmonicity coupling with other phonons.

${\text{BiFeO}}_3$ (BFO), ${\text{BiFe}}_{1-x}{\text{Ti}}_x{\text{O}}_3$ , and ${\text{BiFe}}_{0.9}{\text{Ti}}_{0.05}{\text{Co}}_{0.05}{\text{O}}_3$ thin films were deposited on $\text{Pt}/{\text{TiO}}_2/{\text{SiO}}_2/\text{Si}$ substrates by chemical solution deposition. BFO film has distorted rhombohedral $R_{3c}$ structure and in ${\text{BiFe}}_{1-x}{\text{Ti}}_x{\text{O}}_3$ (104)/(110) reflections broadened suggesting limited grain growth with Ti substitution. The surface roughness (rms) decreased in the case of Ti substituted BFO. Up to 5% Ti in the lattice reduces the leakage current substantially. For ${\text{BiFe}}_{1-x}{\text{Ti}}_x{\text{O}}_3$ , the leakage current qualitatively followed the same trend and the behavior resembles to space charge limited current conduction. The magnetic properties were completely lost by Ti substitution and slightly recovered upon cosubstitution with magnetically active Co. The disappearance of ferromagnetic hysteresis of BFO with Ti substitution and its reappearance with Co is suggestive of the origin of magnetic properties consequential from the BFO lattice itself and hence support it as an intrinsic property of BFO. Capacitance-voltage characteristics of BFO, ${\text{BiFe}}_{0.95}{\text{Ti}}_{0.05}{\text{O}}_3$ , and ${\text{BiFe}}_{0.9}{\text{Ti}}_{0.05}{\text{Co}}_{0.05}{\text{O}}_3$ showed butterfly loop indicating ferroelectric property at room temperature as well as at low temperature. However, saturated polarization-voltage hysteresis was not observed in all cases and ${\text{BiFe}}_{0.9}{\text{Ti}}_{0.05}{\text{Co}}_{0.05}{\text{O}}_3$ films showed very poor ferroelectricity compared to BFO and ${\text{BiFe}}_{0.95}{\text{Ti}}_{0.05}{\text{O}}_3$ .

We report structural, optical, temperature and frequency dependent dielectric, and energy storage properties of pulsed laser deposited (100) highly textured BaZr_xTi_1−xO₃ (x = 0.3, 0.4, and 0.5) relaxor ferroelectric thin films on La_0.7Sr_0.3MnO₃/MgO substrates which make them potential lead-free capacitive energy storage materials for scalable electronic devices. A high dielectric constant of ∼1400–3500 and a low dielectric loss of <0.025 were achieved at 10 kHz for all three compositions at ambient conditions. Ultrahigh stored and recoverable electrostatic energy densities as high as 214 ± 1 and 156 ± 1 J/cm³, respectively, were demonstrated at a sustained high electric field of ∼3 MV/cm with an efficiency of 72.8 ± 0.6% in an optimum 30% Zr substituted BaTiO₃ composition.

Multilevel resistive switching was observed in random access memory device using amorphous SmGdO₃ (SGO) ternary oxide thin films. Non-volatile and stable 4-level resistance states with sufficient margin of resistance ratios were observed by varying compliance current which was attributed to compliance current dependent variation in size of conducting filaments. As fabricated Pt/SGO/Pt devices exhibited excellent switching parameters such as stable resistance ratios of reset (ON) to set (OFF) states, non-overlapping switching voltages, excellent data retention, and endurance. Temperature dependent variation of resistances of ON and OFF states of the device was studied to elucidate current conduction and resistive switching mechanisms.

We report a remarkable photovoltaic effect in pulsed laser deposited multiferroic aurivillius phase Bi₅FeTi₃O₁₅ (BFTO) thin films sandwiched between ZnO:Al transparent conductive oxide top electrode and SrRuO₃ bottom electrode fabricated on amorphous fused silica substrates. The structural and micro structural properties of these films were analysed by X-ray diffraction and atomic force microscopy techniques. The films were showing a photo sensitive ferroelectric behaviour with a notable apparent polarization in the range of 10–15 μC/cm². These films also exhibited a switchable photo-response and this parameter was observed to be sensitive to polarisation field and the polarization direction. The device shows a large ON/OFF photo current ratio with an open circuit voltage of 0.14 V. The photo response at zero bias of this BFTO based heterostructures showed rapid increase to a saturation value of 6 μA at zero bias.