S. L. Gupta

Ferroelectric photovoltaic properties of Ce and Mn codoped BiFeO3 thin film

Photovoltaic properties of multiferroic (Ce, Mn) codoped BiFeO3 (BCFMO) thin films grown on low cost ITO coated corning glass substrate have been investigated. The transient response of photovoltaic current of the BCFMO thin film in metal-multiferroic-metal (MMM) capacitor configuration is found to be strongly dependent on both the intensity of incident laser light (λ = 405 nm) varying from 15 mW/cm2 to 160 mW/cm2 and thickness of the BCFMO film (110 to 305 nm). Current density-voltage (J-V) measurement shows an exponential increase in photoinduced open circuit voltage and linear increase in short circuit photocurrent with increase in intensity of illuminating light. Almost 240 fold enhancement in photo-induced current is observed in BCFMO thin film of 110 nm thickness. Present work suggests that multiferroic BCFMO thin film deposited on ITO coated corning glass substrate using chemical solution deposition technique exhibits strong photovoltaic response that can be exploited efficiently for the light harv...

Piezoresponse force microscopy and vibrating sample magnetometer study of single phased Mn induced multiferroic BiFeO3 thin film

The effect of Bi excess (0 to 15%) and subsequently Mn doping (0 to 20%) on the structural, ferroelectric, and magnetic properties of BiFeO3 (BFO) thin films deposited by chemical solution deposition technique on low cost substrates are reported in the present work. No significant changes in crystallographic structure of BFO were observed with 5% excess Bi. With further increasing the Bi concentrations (> 10%), however, rhombohedral phase transformation occurs with appearance of the other Bi excess phases. Piezoresponse force microscopy studies show that the BFO thin film having 5% excess Bi and 10% Mn yields good ferroelectric behavior. The ferromagnetic behavior of 10% Mn doped BFO thin film is confirmed with vibrating sample magnetometer studies. The results indicate that the 10% Mn doped BFO thin films deposited by chemical solution deposition technique on low cost substrate exhibit very good multiferroic properties, suitable for magnetic memories applications.

Optimization of excess Bi doping to enhance ferroic orders of spin casted BiFeO3 thin film

Multiferroic Bismuth Ferrite (BiFeO3) thin films with varying excess bismuth (Bi) concentration were grown by chemical solution deposition technique. Room temperature multiferroic properties (ferromagnetism, ferroelectricity, and piezoelectricity) of the deposited BiFeO3 thin films have been studied. High resolution X-ray diffraction and Raman spectroscopy studies reveal that the dominant phases formed in the prepared samples change continuously from a mixture of BiFeO3 and Fe2O3 to pure BiFeO3 phase and, subsequently, to a mixture of BiFeO3 and Bi2O3 with increase in the concentration of excess Bi from 0% to 15%. BiFeO3 thin films having low content (0% and 2%) of excess Bi showed the traces of ferromagnetic phase (γ-Fe2O3). Deterioration in ferroic properties of BiFeO3 thin films is also observed when prepared with higher content (15%) of excess Bi. Single-phased BiFeO3 thin film prepared with 5% excess Bi concentration exhibited the soft ferromagnetic hysteresis loops and ferroelectric characteristics with remnant polarization 4.2 μC/cm2 and saturation magnetization 11.66 emu/g. The switching of fine spontaneous domains with applied dc bias has been observed using piezoresponse force microscopy in BiFeO3 thin films having 5% excess Bi. The results are important to identify optimum excess Bi concentration needed for the formation of single phase BiFeO3 thin films exhibiting the improved multiferroic properties.

Raman spectroscopy of nanocrystalline Mn-doped BiFeO3 thin films

Enhancement of magnetic and electric properties in multiferroic Mn-substituted BiFeO3 thin films (BiFe1− x Mn x O3 with x = 0.00–0.05) grown via the low-temperature chemical solution deposition process on low-cost substrates like indium tin oxide (ITO)/glass and silicon is reported in this work. A detailed structural analysis by high-resolution X-ray diffraction and Raman spectroscopy indicates that the grown films exhibit rhombohedral distorted perovskite structure without any impure phase. Raman spectroscopic analysis shows all 13 Raman active (4A1 + 9E) phonon modes corresponding to distorted rhombohedral BFO R3c structure. BFO thin film with 5% Mn substitution showed maximum saturation and remnant magnetisation (M s = 16.70 emu/g and M r = 2.58 emu/g) and remarkably reduced leakage current due to distortion in the spin cycloid structure and suppression of oxygen vacancies due to partial replacement of Fe3+ ion by Mn3+ ion, respectively. These enhanced multifunctional properties highlight the potential applications of BFMO system in thin film devices which can couple magnetic and ferroelectric order parameters.

Study of A-site and B-site Doping on Multiferroic Properties of BFO Thin Films

The 12% Cerium (Ce) and 10% Manganese (Mn) were doped at A and B sites respectively in BiFeO3 (BFO) thin films along with incorporation of 5% excess Bi. Pure and undoped BFO thin film capacitors are fabricated on indium tin oxide (ITO) coated corning glass and silicon substrate by chemical solution deposition (CSD) method. Film becomes preferred oriented along (110) directions with introduction of Mn and Ce in the host BFO lattice. Leakage current density is reduced by about 4 orders from (4.59 × 10−3 A/cm2) to about 2.91 × 10−7 A/cm2 at 100 KV/cm field after 12% Ce doping in BFO (BCFO) thin film. Enhanced ferroelectric response with saturated P-E loop is observed for BCFO thin film in compare to that obtained for 10% Mn doped BFO (BFMO) thin film. Improved capacitance-voltage characteristics with good butterfly loop is obtained for Bi0.88Ce0.12FeO3 thin film, indicating an increased degree of ferroelectricity. However, enhanced M-H loop with well saturation magnetization (Ms ∼ 19.65 emu/g) is observed for BFMO thin films while wasp waist loops (pinched) are observed for BCFO thin films with slightly degraded ferromagnetic properties.

High-Spin States in Odd–Odd 168Lu

Abstract: High-spin states in the odd-odd 168Lu nucleus, populated in the 154Sm(19F,5n) reaction at a beam energy of 96 MeV, were investigated using in-beam γ-ray spectroscopy techniques. The BC neutron crossing in the yrast band, based on πg7/2[404]7/2+⊗νi13/2[642]5/2+ configuration, occurs at ħω= 0.31 MeV. The two side bands, based on πh11/2[514]9/2−⊗νi13/2[642]5/2+ and πh9/2[541]1/2−⊗νi13/2[642]5/2+ configurations, show anomalous signature-splitting and signature-inversion in the first one, to occur at ħω= 0.24 MeV. A moderately delayed BC-crossing is anticipated in the second one.

Internal conversion coefficients ofM4 transitions in125m, 127m, 129mTe decay

The internal conversion coefficients have been measured using a high resolution low energy Ge(Li) detector for the followingM4 transitions:125Te: 109.27keV transitionαT=357±11; RG method,127Te: 88.26 keV transitionαT=484±23; XPG method,129Te: 105.50keV transitionαT=213±10; XPG method.It is observed that these values are lower by 2.5–3.6% as compared with Hager and Seltzers calculations. A comparison between experimental and theoreticalαT andαT values for elevenM4 transitions shows that the experimental values are systematically lower.

Enhanced Magnetic and Electric Properties of Nanocrystalline Ce Modified BFO Thin Films

Ce modified bismuth ferrite (Bi1−xCexFeO3, BCFO) thin films were prepared by a chemical solution deposition method with the value of x varying from 0 to 0.08. Structural, morphological, electrical and magnetic properties of the deposited BCFO thin films have been characterized. Partial introduction of Ce at Bi lattice sites not only reduces the leakage current densities remarkably up to 3 order in magnitude at higher electric field but also substantially improves the saturation magnetization MS (12.8 emu/cm3) with anomalous pinched off (wasp-waist shaped) M-H hysteresis loop showing spin coupling interaction. The breakdown field also enhanced in the BFO films with Ce substitution.

Surface plasmon resonance based electro optic measurement of SBN thin films

Strontium Barium Niobate (SBN) has been known for its highest electro optic coefficient amongst the known photorefractive materials. SBN thin films were prepared using Pulsed Laser Deposition (PLD) technique on the conducting LSCO coated Si Substrate and its tetragonal tungsten bronze structure was confirmed using X-ray diffraction technique. Surface Plasmon Resonance (SPR) technique has been effectively used by exploiting the SBN thin film in Otto configuration using prism coupling technique. The SPR reflectance curves for prism/air-gap/gold/SBN/LSCO/Si system were obtained by varying the applied electric field from 0 to 150kV/cm. A continuous increase in minimum reflectance of SPR curves with increase in the electric field across the SBN thin film has been obtained indicating variation in optical properties of SBN thin film on application of electric field. This increase in reflectance was attributed to the change in propagation constant of wave vector due to the change of optical properties of the film under consideration. The resonance condition changes hence the SPR minimum reflectance angle and position changes.

Study of ferroelectric SBN thin films for electro-optic applications

The Ferroelectric strontium barium niobate (SBN) thin films are prepared using Pulsed Laser Deposition (PLD) technique. XRD spectra of the prepared films indicate the polycrystalline growth confirming the formation of tetragonal tungsten bronze structure. A waveguide is fabricated so as to guide the light in SBN thin film. The EO measurements for the SBN thin films have been carried out using Senarmont Compensation method in order to examine the dynamic variation of EO coefficient of the prepared films. The value of dynamic EO coefficient is found to be 198pm/V.