Keywords : Multiferroic

Synthesis and characterization of pure BiFeO3 using various complexing agents by Sol-gel method

Balesh Kumar Vashisth; Jarnail S. Bangruwa; S. P. Gairola; Vivek Verma

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 805-810
DOI: 10.5185/amlett.2018.2173

Pure BiFeO3 (BFO) nanoparticles were prepared using various complexing agents like citric acid, malonic acid, succinic anhydride and tartaric acid by sol-gel method annealed at different temperatures (400 °C, 500 °C, 600 °C). X-Ray diffraction pattern of various samples show the degree of formation of required phase. Particle size of pure phase BFO has been shown using TEM image. Scanning Electron Microscopy studies for different samples give detailed study of morphology of samples. Ferroelectric and magnetic studies of best prepared samples show their comparative multiferroic properties. Dielectric analysis also shows the variation in dielectric loss, real and imaginary part of permittivity versus frequency at room temperature.

Study Of A-site Divalent Doping On Multiferroic Properties Of BFO Nanoparticles Processed Via Combustion Method

Baljinder Kaur; Lakhbir Singh; V. Annapu Reddy; Dae-Yong Jeong; Navneet Dabra; Jasbir S. Hundal

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 1015-1020
DOI: 10.5185/amlett.2016.6457

Pure and Sr?doped bismuth ferrite Bi1-xSrx FeO3 (x = 0, 0.1, 0.2, 0.3) nanoparticles have been synthesized using combustion method. X- Ray diffraction study of these compounds confirms the rhombohedral structure with R3c space group. BiFeO3 peaks were observed at 2θ = 22.46o, 31.80o, 32.11o, 39.519o, 45.79o, 51.35o, 56.98o and 57.16o having miller indices as (012), (104), (110), (202), (024), (116), (214) respectively. The traces of secondary phase also appear along with desired phase of Sr?doped bismuth ferrite Bi1-xSrxFeO3 samples. The scanning electron microscopy of fractured pellets of the samples reveals the decrease in grain size with increase of Sr doping in Bi1-xSrxFeO3. Magnetic studies were carried out at room temperature up to a field of 10 kOe. M-H hysteresis loops showed a significant increase in magnetization with Sr substitution in BiFeO3. Compared to weak magnetisation with magnetizing field (M-H) shown by BiFeO3 nanoparticles (Remnant magnetization, Mr ~ 0.4x10-3 emu/g and coercive field, Hc ~ 0.065 kOe respectively), a significant enhancement in M-H loop was observed in Bi1-xSrx FeO3 compounds. The value of Mr ~ 0.525 emu/g and Hc ~ 3.70 kOe have been found to be maximum for x = 0.30 in Bi1-xSrx FeO3 compounds. Leakage current studies showed decrease in leakage current density of doped samples to that of pure BiFeO3 and x = 0.10 gives minimum value of 4.78 x 10-6 A/cm2 at 350 V/cm. The ferroelectric nature was confirmed by observed P-E loops in all the samples.

Multiferroic Properties In Nanostructured Multilayered Magnetic Semiconductor Bi0.9La0.1Fe0.9Co0.1O3-BiFeO3 Thin Films

V. Annapu Reddy; Navneet Dabra; K. K. Ashish; Jasbir S. Hundal; N. P. Pathak; R. Nath

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 678-683
DOI: 10.5185/amlett.2015.5802

Multilayers with nanostructured thin films of Bi0.9La0.1Fe0.9Co0.1O3-BiFeO3 (BLFCO-BFO) were grown on Zn0.91Mn0.09O (ZMO) buffered Si (100) substrate by chemical solution deposition. Structural analysis indicates that rhombohedral crystal structure of BFO, changes to orthorhombic for BLFCO film. Increased ferroelectric saturation and reduced leakage current were obtained for bi-layered and four-layered thin films and are compared with those of BFO and BLFCO thin films.Improvement in ferroelectric properties, as well as induced ferromagnetism was enhanced for four-layered thin films than two-layered thin films. The interface coupling and interaction between the thin layers has led to the resultant improvements. Highly enhanced ferroelectric fatigue properties are observed in these multilayer films up to 10 8 switching cycles.

Structural, Dielectric And Magnetic Properties Of 0.3CoFe2O4-0.7BaTiO3-PVDF Composite Film

Manjusha and K.L. Yadav; Manjusha;K.L. Yadav

Advanced Materials Letters, 2014, Volume 5, Issue 11, Pages 652-657
DOI: 10.5185/amlett.2014.4567

Structural, Dielectric and magnetic properties 0.3 CoFe2O4–0.7 BaTiO3–PVDF (polyvinylidene fluride) composite film with different concentration of PVDF: 20, 30 and 40 wt% are reported here for the first time. The structural analysis was carried out using X-Ray diffraction technique, which indicates cubic spinel structure for ferrite phase CoFe2O4 (CFO) and tetragonal structure for ferroelectric phase BaTiO3 (BT). The average grain size was observed to be (~106 nm, 30 nm and 26 nm) for 20%, 30% and 40% addition of PVDF by using AFM analysis. The dielectric constant variation with temperature at three fixed frequencies (1 kHz, 50 kHz and 100 kHz) was studied and it was found that the dielectric constant and dielectric loss decrease with increasing amount of polyvinylidene fluride. The values of ac conductivity for 0.3CoFe2O4 – 0.7BaTiO3 –PVDF composite film were found to decrease with increasing concentration of PVDF. The ferroelectric hysteresis loops also indicate that the value of polarization decreases with the addition of PVDF and the value of remnant polarization for 20% PVDF was found to be 0.5286 µC/cm 2 . The magnetocapacitance of 0.3 CoFe2O4–0.7 BaTiO3–0.3 PVDF was found higher for this composition.

Preparation and Studies on (1-x) BiFeO3–x Li0.5Fe2.5O4 (x=0.25 And 0.5) multiferroic nano-composites 

Samar Layek; Soumen Kumar Bag;H.C. Verma

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 26-30
DOI: 10.5185/amlett.2013.icnano.289

Multiferroic nano-composite (1-x) BiFeO3–x Li0.5Fe2.5O4 (x=0.25 and 0.5) have been successfully synthesized by mixing the two phases, prepared independently by two different methods followed by annealing at 600 0C. Existence of the two phases in the composite is confirmed by x-ray diffraction pattern. Average particle size is calculated to be about 45 nm for both of these phases. The saturation magnetization, remnant magnetization and coercive field increases linearly with increasing ferromagnetic phase (Li0.5Fe2.5O4) as investigated by VSM measurement. Local magnetic behaviors have been investigated by 57Fe Mössbauer spectroscopic studies. Large dielectric constant of the order of 10 3 -10 4 has been observed in these composites.

Magnetic And Dielectric Properties Of Multiferroic BiFeO3 nanoparticles Synthesized By A Novel Citrate Combustion Method

Samar Layek;H.C. Verma

Advanced Materials Letters, 2012, Volume 3, Issue 6, Pages 533-538
DOI: 10.5185/amlett.2012.icnano.242

Single phase BiFeO3 nanoparticles have been successfully synthesized for the first time by a novel citrate combustion method without using any solvent. Well mixed metal nitrates along with citric acid which is used as fuel combust to give BiFeO3 nanoparticles after annealing. These particles are single phase in nature and crystallize in the rhombohedral distorted perovskite structure (space group-R3c) which has been confirmed by the Rietveld refinement of the room temperature powder x-ray diffraction data. Nearly spherical particles of average particle size 47 nm have been seen from transmission electron micrograph. Room temperature magnetic hysteresis measurement shows weak ferromagnetism though the magnetization does not saturate upto 1.75 T applied field. The coercive field value is calculated to be 180 Oe which is 3 times higher than that prepared by solvent free combustion method using glycine. 57 Fe Mössbauer spectrum can be fitted with a sextet corresponding to single magnetic state of hyperfine field about 49.5 T corresponding to Fe 3+ state of the iron atom. The dielectric relaxation and ac conductivity as a function of frequency have been discussed. High dielectric permittivity has not been found in these nanoparticles like other reported BiFeO3  ceramics.

Magnetoelectric Coupling In Multiferroic Ba(Fe0.01Ti0.99)O3 nanowires

Jaspreet Kaur; Jasneet Kaur; Jyoti Shah; R.K. Kotnala; Vinay Gupta; Kuldeep Chand Verma

Advanced Materials Letters, 2012, Volume 3, Issue 5, Pages 371-375
DOI: 10.5185/amlett.2012.5352

In the present work, structural, microstructural and magnetoelectric (ME) coupling of multiferroic Ba(Fe0.01Ti0.99)O3 (BFT1) nanowires have been studied. BFT1 nanowires were prepared by a hydrothermal method with reaction temperature 180 o C for 48 hours. The X-ray diffraction shows that BFT1 is polycrystalline with cubic phase. The calculated value of distortion ratio (c/a) is ~ 1. No impurity or extra phase is observed. The micrographs by transmission electron microscopy reveal nanowires like structure of BFT1with diameter lie in the range of ~ 40 - 50 nm and length greater than 1.5 μm. The ME coefficient measurement shows that the ME coupling under the effect of both ac and dc bias. It shows strong dependence on ac and dc bias applied field. The value of linear coefficient (α) called ME coefficient is calculated as ~ 16 mV/Oecm at a fixed frequency of 850 Hz. This ME coefficient α corresponds to induction of polarization by a magnetic field or of magnetization by an electric field. The observed optimum dc bias field at which the maximum magneto-electric coupling occurs is ~ 750 Oe. The magnetization hysteresis shows strong ferromagnetism.