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Poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) based pyroelectric as well as magnetoelectric materials offer great promises for energy harvesting for flexible and wearable applications. Hence, this work focus on solar energy harvesting as well as magnetoelectric phenomenon in two phase nanocomposite film where the constituting phases are manganese ferrite (MnFe2O4) nanoparticles and P(VDF-TrFE) polymer. Composite films have been prepared using solution casting technique. X-ray diffraction result shows higher crystallinity of these films. The ferroelectric, magnetic and magnetoelectric properties in variation with applied field and volume percentage of ferrite nanoparticles have been investigated. The preparation condition was optimized in such a way that it results improved ferroelectric polarization of nanocomposite film after incorporation of small amount of ferrite nanoparticles. The maximum magnetoelectric-coupling coefficient of about 156 mV/Oe-Cm was obtained for optimum nanocomposite film when DC bias field was applied perpendicular to electric polarization direction. From a pyroelectric device perspective, solar energy harvesting is also reported. An open circuit voltage of 5V and short circuit current of order of ~1 nA is demonstrated without any pre amplification. Hence, the combination of magnetoelectric and pyroelectric properties of nanocomposite film presented here indicate as a perfect candidate for smart materials, spintronics devices and specified magnetoelectric-based applications.

The existence of magnetostriction in bulk BiFeO3 is still a matter of investigation and it is also an issue to investigate the magnetostriction effect in nano BiFeO3. Present work demonstrates the existence of magnetostrictive strain in superparamagnetic BiFeO3 nanoparticles at room temperature and the magnetoelectric coupling properties in composite form with P(VDFTrFE). Despite few reports on the magnetostriction effect in bulk BiFeO3 evidenced by the indirect method, the direct method (strain gauge) was employed in this work to examine the magnetostriction of superparamagnetic BiFeO3. In addition, a high magnetoelectric coupling coefficient was observed by the lock-in technique for optimized BiFeO3_P(VDF-TrFE) nanocomposite film. These nanocomposite films also exhibit room-temperature multiferroic properties. These results provide aspects of material with immense potential for practical applications in spintronics and magneto-electronics applications. We report a magnetoelectric sensor using superparamagnetic BiFeO3_P(VDF-TrFE) nanocomposite film for detection of ac magnetic field.

We have investigated the coupling of lattice with spin via strain interactions in the CoFe2O4/PMN-PT composite system. X-ray diffraction and Raman spectroscopic studies illustrate a remarkable modification in CoFe2O4lattice across Curie temperature (450 K) of PMN-PT. Subsequently, CoFe2O4/PMN-PT composite reveals a sudden drop in magnetic moment across Tc of PMN-PT (450 K). However,theindependent CoFe2O4phasedisplaystypical ferromagnetic behaviour across this temperature. These findings establish spin-lattice coupling owing to th interfacial strain transfer between CoFe2O4 and PMN-PT in composite. The strain intractions leads to magneto-electric coupling, evidenced by measuring magentization and magneto-electric coefficient for the electric field poled and unploed CoFe2O4/PMN-PT composite samples. X-ray magnetic circular dichroism (XMCD) analysis establishes that the cation (Fe3+/Co2+) redistribution occurs on tetrahedral and octahedral site in the electrically poled CoFe2O4/PMN-PT composite, confirming the coupling between magnetic and electric ordering in the composite. The magneto-electric coupling coefficient alpha vs dc magnetic field curves revealed hysteretic behavior and enhanced {\alpha} values after electric poling, which originates from the strain induced modifications in the magnetic domains configuration of composite in the poled samples. These findings suggest that the existence of spin lattice coupling may leads to the mechanism of strong magneto-electric effects via strain interactions in CoFe2O4/PMN-PT composite., Comment: 26 pages, 9 figures

We have explored the electric field controlled magnetization in the nanodot CoFe2O4/SrRuO3/PMN-PT heterostructures. Ordered ferromagnetic CFO nanodots (~300 nm lateral dimension) are developed on the PMN-PT substrate (ferroelectric as well as piezoelectric) using a nanostencil-mask pattering method during pulsed laser deposition. The nanostructures reveal electric field induced magnetization reversal in the single domain CFO nanodots through transfer of piezostrains from the piezoelectric PMN-PT substrate to the CFO. Further, electric field modulated spin structure of CFO nanomagnets is analysed by using X-ray magnetic circular dichroism (XMCD). The XMCD analysis reveals cations (Fe3+/Co2+) redistribution on the octahedral and tetrahedral site in the electric field poled CoFe2O4 nanodots, establishing the strain induced magneto-electric coupling effects. The CoFe2O4/SrRuO3/PMN-PT nanodots structure demonstrate multilevel switching of ME coupling coefficient ({\alpha}) by applying selective positive and negative electric fields in a non-volatile manner. The retention of two stable states of {\alpha} is illustrated for ~106 seconds, which can be employed to store the digital data in non-volatile memory devices. Thus the voltage controlled magnetization in the nanodot structures leads a path towards the invention of energy efficient high-density memory devices., Comment: 19 pages, 5 figures

The transparent Er, Nd co-doped Yttria ceramics with transparency around 78 percentage (in 500 - 2000 nm range without Fresnels correction) were fabricated successfully. It involved nanoparticle synthesis by coprecipitation method and sintering of pellets under high vacuum condition. The crystalline phase, particle size and element composition were confirmed by X- ray diffraction, scanning electron microscope, energy dispersive X- ray fluorescence techniques, respectively. The upconversion luminescence mechanisms involving energy transfer and non-radiative relaxation were analyzed. It is expected that, the result evolved from this study will provide better understanding of upconversion mechanism involved in Er, Nd codoped host material. The emission at both 563 nm and 1064 nm on 822 nm excitation proves potential of the ceramic material for dual mode efficient emitter., Comment: 21 pages with 9 figures

The photoluminescence properties of Yb doped Y2O3 nanoparticles are investigated in visible region. The presence of peaks at 335 nm and 370 nm in the excitation spectra of bulk as well as in nano Yb: Y2O3 and their absence in pure Y2O3 confirm its origin due to Yb3+ dopant. The Yb doping in nano Y2O3 not only modify the charge transfer bands (CTB) but also helps in transition of electron from these CTBs to ground 2F5/2 and 2F7/2 levels of Yb. This results in strong intense broad emission from ~400 to ~650 nm (white light emission range) for 335 nm excitation., Comment: 22 pages 8 figures

Nanophosphors of (Sr0.98-xMgxEu0.02)2SiO4 (x=0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation but the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore the (Mg0.78Sr0.20Eu0.02)2SiO4: Eu2+ nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green-yellow emission at 395 nm excitations. The CIE coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in 1: 1 ratio) falls in the white region demonstrating the possible use of the mixture in white light generation using near UV excitation source., Comment: 22 pages, 9 figures

The influence of La and Nd co-substitution on the structural and magnetic properties of BiFeO3 (BFO) thin films was examined. Epitaxial thin films of pure and, La and Nd co-doped BFO on the SrRuO3 buffered single crystal SrTiO3 (001) substrate were deposited using pulsed laser deposition. The structural change in co doped La and Nd BFO thin films which was caused by the changes of force constant in the crystal lattice induced by ionic radii mismatch was investigated. Raman spectroscopy studies manifest the structural change in doped BFO films from rhombohedral to monoclinic distorted phase which is induced by the co substitution of La and Nd. Room temperature magnetic hysteresis curves indicated that saturation magnetization is enhanced in the doped film with saturation magnetization of ~20 emu/cm3. The dielectric and magnetic properties are effectively improved in BLNFO films compared to pure BFO thin films., Comment: 11 figures 31 pages

The Poly(vinylidene fluoride)/CaCu3Ti4O12 (CCTO) nanocrystal composite films (85nm) with relatively high dielectric permittivity (90 at 100Hz) were prepared by the solution casting followed by spin coating technique. The structural, the microstructural and the dielectric properties of the composites were studied using X-ray diffraction, Scanning Electron Microscope, and Impedance analyzer respectively. The effective dielectric permittivity of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz to 1MHz) under investigation. The room temperature dielectric permittivity which is around 90 at 100Hz, has increased to about 290 at 125oC (100Hz). These results may be exploited in the development of high energy density capacitors.

For pyroelectric detector application materials should have low dielectric constant, high pyroelectric coefficient, large non volatile polarization at small applied electric field and low specific heat. Large field (greater than 1200kV/cm) is need to pole ferroelectric polymer poly (vinylidene fluoride) (PVDF) and it has low sensitivity compared to other pyroelectric materials. To increase non volatile polarization at low poling field and to increase pyroelectric coefficient, LiTaO3 (LT) nano particles were added to PVDF matrix to make LT/PVDF composite. It is important to study the dielectric properties of the composite (to be used in detector application) because dielectric constant varies with volume fraction of filler and with frequency. Nano composite films of LT/PVDF with different volume fraction (i. e fLT = 0.047, 0.09 and 0.17) of LT were prepared by dispersing LT nano particles in solution of PVDF. The dielectric properties of LT/PVDF composite were studied by varying the volume fraction of LT. The dielectric permittivity of LT/ PVDF composites increased compared to PVDF as the volume fraction of LT increases but the loss tangent is almost constant at higher frequency. In low frequency region, for fLT = 0.17 the dielectric permittivity of composite is greater than PVDF and LT. The dielectric loss tangent is also increased from 0.04 to 0.175 as fLT increases from 0 to 0.17 at 1 kHz. The dielectric permittivity behavior of composite has been explained using percolation model and space charge polarization model., Comment: Please send your comments(20 pages with figures)

For pyroelectric sensor application, materials having large ferroelectric polarization at low applied field and high pyroelectric sensitivity are required. PVDF is one of the ferroelectric polymers, which is being used for pyroelectric detector application. Following properties of PVDF such as low density, low acoustic impedance, wide bandwidth, flexibility, toughness, and ease of fabrication into complex patterns and arrays make it suitable for large area detector applications. But the PVDF has low value of pyroelectric coefficient (p). High field (above 1200kV/cm) is required to pole the PVDF film. To reduce poling field and to get high value of ferroelectric polarization at low poling field, nano composite films of LT/PVDF have been prepared. Since LT is ferroelectric (max. poling field ~ 200kV/cm and (p) ~ 2.3 * 10-8 C cm-2/ K) in nature, the nonvolatile polarization of composite increased from 0.014microC/cm2 to 2.06microC/cm2 at an applied field of 150kV/cm as the volume fraction of LT (fLT) nano particle increases from 0.0 to 0.17. Similarly the increase of fLT from 0.0 to 0.17 results in increase of pyroelectric voltage sensitivity from 3.93 V/J to 18.5V/J., Comment: please send your comments(18 pages including figures)

In literature it has been reported that the gamma-phase PVDF film is formed from dimethyl sulfoxide (DMSO) solvents regardless of preparation temperature. In this report the crystallization of both alpha and gamma phase from DMSO solvent by varying preparation temperature has been described. This paper also describes the conversion of gamma-phase to beta- phase and alpha-phase at different annealing condition. When thin films were annealed at 90C for 5 hours, then maximum beta-phase content (greater than 95%) is present in PVDF thin film. The PVDF films completely converted to alpha-phase, when they were annealed at 160C for 5 hours. From (X-ray diffraction) XRD, Fourier Transform Infrared Spectrum (FTIR), (Differential thermal analysis) DTA and Raman studies, it is confirmed that the PVDF thin films, cast from DMSO solution and annealed at 90C for 5 hours, have maximum percentage of beta-phase(greater than 95%)., Comment: please send your comments(18 pages including figures)

Structural, electrical and magnetic properties of Bi0.9-xLa0.1ErxFeO3 (BLEFOx) (x = 0.05, 0.07, 0.1) polycrystalline ceramics prepared by solid solution route were studied. A phase transition from rhombohedral phase to monoclinic phase was observed for x=0.05-0.1 in (BLEFOx). We have measured phase transition temperatures both alpha-beta transition and low-Temperature (low-T) transitions in doped BiFeO3. The transition peak near to 835C corresponds to alpha to beta-phase transition of BiFeO3 were measured using diffential thermal analysis (DTA). Dielectric measurements shows the low-T transitions in BLEFOx (x = 0.05-0.1). Relatively high remanent magnetization of 0.1178emu/gm at 8T was observed in BLEFOx (x = 0.1)., Comment: Please mail your comments to srinu73@cat.ernet.in

Resonant Raman spectra (RRS) of O-H and O-D vibration and libration modes, their combinations and higher harmonics have been observed in LiTaO3 polycrystalline thin films. RRS peaks are superimposed on photoluminescence (PL) spectrum. Monochromatic light from a xenon lamp is used as excitation source. PL spectrum shows two broad peaks, first near the band gap in UV (4.4-4.8eV) and another in the sub band gap region (< 4.0 eV). Band gap PL along with RRS peaks are reported for the first time. Photoluminescence excitation spectrum (PLE) shows a peak at 4.8 eV. Peak positions and full width at half maximum (FWHM) of RRS peaks depend upon the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O-H with excitation energy are about 800 cm-1/eV and 2000 cm-1/eV respectively. This dispersion is much higher than reported in any other material., Comment: 20 pages