Jashashree Ray - Academia.edu (original) (raw)
Papers by Jashashree Ray
Journal of Applied Physics, 2015
Dielectric and magnetodielectric measurements are done on BiFe1−xCoxO3: x = 0, 0.01, and 0.02 in ... more Dielectric and magnetodielectric measurements are done on BiFe1−xCoxO3: x = 0, 0.01, and 0.02 in the temperature range 70–300 K and up to magnetic field 1.3 T. The dielectric data are well described by Haverliak–Negami expression plus an additional term for the Maxwell Wagner (MW) type relaxations, whose contribution is dominant near room temperature. The parameters obtained from the fitting of data using the above mentioned expression, suggest slowing down of relaxation and approach towards ideal Debye type relaxations, as the temperature is lowered. The dielectric relaxations obey polaronic variable range hopping model with distinct activation energies (Ea) in the extrinsic (6.67T3/4 meV) and intrinsic (2.88T3/4 meV) regions for the parent sample (x = 0), and thus a distinct transition from extrinsic to intrinsic behavior is seen at 215 K while lowering the temperature. This distinct transition is missing for Co substituted samples probably due to the extrinsic region values of Ea...
Journal of Alloys and Compounds, 2015
Bi 13 Co 12)CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5)CoO 40 (BCFO) nanoparticles are prepared by sol... more Bi 13 Co 12)CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5)CoO 40 (BCFO) nanoparticles are prepared by sol-gel auto combustion method. The x-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100nm to 75nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30K, which seems to be competing paramagnetic and antiferromagnetic behaviour. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, throughout the temperature range for BCO. For BCFO, the behaviour may be divided under two regions viz., intrinsic (< 260K) and extrinsic (> 260K). Relaxation in both the regions is described by Arrhenius behaviour with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak-Negami equation is found to better describe the observed relaxation data. Highlights • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen.
Solid State Communications, 2015
Journal of Applied Physics, 2015
In the continuation of our previous work [Biswal et al., J. Appl. Phys. 115, 194106 (2014)] of bi... more In the continuation of our previous work [Biswal et al., J. Appl. Phys. 115, 194106 (2014)] of biphasic La2NiMnO6 (LNM) prepared via sol-gel technique, here we are reporting the effect of Cu substitution at Ni site of LNM. The powder x-ray diffraction results of La2Ni1−xCuxMnO6 (x = 0, 0.05, 0.1) confirm the biphasic nature (Pbnm + R-3c) for all samples along with increasing R-3c phase with Cu content in the sample. The temperature variation of magnetization (M) plot shows sharp ferromagnetic transitions of R-3c phase at 285 K, 278 K, and 270 K (obtained from dM/dT plot) and that of Pbnm phase at 165 K, 145 K, and 145 K for x = 0, 0.05, and 0.1, respectively. Weak antiferromagnetic type feature at 25 K (x = 0), is getting pronounced with Cu content in the sample and is now seen at 32 K & 266 K (for x = 0.05) and 32K & 257 K (for x = 0.1). Fitting of Curie-Weiss law in the paramagnetic region of χ−1 vs T plot results slightly lower values of corresponding Tc's of R-3 c phase (277...
Journal of Alloys and Compounds, 2015
Room temperature magnetoelectric (ME) measurements are carried out on phase pure BiFeO 3 and BiFe... more Room temperature magnetoelectric (ME) measurements are carried out on phase pure BiFeO 3 and BiFe 0.98 Co 0.02 O 3 , prepared via sol-gel technique. At zero magnetic field, the longitudinal ME coupling coefficient (α) for BiFeO 3 is found to be α = 20.935, which decreases on application of magnetic field and displays hysteresis in magnetic field (H) for the increasing and decreasing cycle of H. This hysteresis disappears for BiFe 0.98 Co 0.02 O 3 and α becomes linear in H along with 17% drop in the magnitude compared to parent BiFeO 3. In spite of 17% drop, magnitude of α = 17.375 is good enough for device applications especially where α must follow the applied magnetic field linearly, e.g., transistors, transducers, etc. Neutron diffraction studies show lattice stiffening due to cobalt substitution in BiFeO 3 and likely to be the cause of disappearance of hysteresis in α. Calculated value of polarization P (using the parameters derived from neutron diffraction) shows 19% drop in magnitude of P for cobalt substituted sample. Surprisingly, dielectric measurements also showed 18% decrease in dielectric constant ' ε due to cobalt doping. Such a one to one correspondence in the three parameters viz., α, P and ' ε , reflects a strong interdependence so that variation in any one of them is reciprocated in the other. Room temperature magnetodielectricity of 5% and 3.2% is observed for BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively. Interestingly similar to α, ߝ ᇱ also shows hysteresis in magnetic field for BiFeO 3 and the hysteresis disappears for BiFe 0.08 Co 0.02 O 3. The dc electrical resistivity measurements, suggests variable range hopping (VRH) with average hopping range 50.038 ܶ .ଶହ ⁄ and 40.058 ܶ .ଶହ ⁄ in BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively, as the conduction mechanism.
AIP Conference Proceedings, 2015
AIP Conference Proceedings, 2015
AIP Conference Proceedings, 2015
Journal of Applied Physics, 2012
The Bi2Sr2CaCu2O8/BiFeO3 (BSCCO/BFO) nano composite for various BFO weight percentage is prepared... more The Bi2Sr2CaCu2O8/BiFeO3 (BSCCO/BFO) nano composite for various BFO weight percentage is prepared and studied for electrical transport. Double resistive superconducting transition is seen in all composite samples with increasing semiconducting nature as a function of BFO content. Initially, the added BFO goes mainly to the grain boundary and from 10% onwards, it enters grains as well, acting as pinning centers. The conduction mechanism in BSCCO shows weak localization for low BFO, tunneling in intermediate BFO, and power law behavior (similar to metal-insulator boundary) for higher BFO samples. The paraconductivity studies reveal the 2D-3D transition in parent BSCCO and the composites, with a signature of percolative behavior in the composites. The study of critical current density reveals two types of Josephson junction in the composites: (1) thin intrinsic superconductor-insulator-superconductor (SIS) type present in all samples including parent BSCCO and (2) extrinsic type due to...
AIP Conference Proceedings, 2013
This thesis presents the study of structural, surface morphology, electric, magnetic, magnetoelec... more This thesis presents the study of structural, surface morphology, electric, magnetic, magnetoelectric and magnetodielectric properties of Cobalt substituted multiferroic BiFeO3. Since their discovery, multiferroics have brought tremendous interest among the researchers due to the coexistence of various ferroic order parameters. The synchronization of the magnetic and electric order parameter, hence generating magnetoelectric coupling, has been of importance in particular. Various functional devices aiming at the coupling between the ferroelectric and ferromagnetic order parameter are underway. Among all, the perovskite oxides (ABO3) based multiferroics are of prime interest due to their ease of synthesis and easy to understand physical interactions due to their simple structure. Bismuth Ferrite (BiFeO3), is a prototype ABO3 type multiferroic material, possessing the ferroelectric Curie temperature (Tc) ~ 1103K and antiferromagnetic Neel temperature (TN) ~ 643K. It exhibits a weak ne...
AIP Conference Proceedings, 2014
ABSTRACT Magnetic relaxation measurements at 5K, 50K and 120K on BiFeO 3 prepared by sol-gel auto... more ABSTRACT Magnetic relaxation measurements at 5K, 50K and 120K on BiFeO 3 prepared by sol-gel auto combustion method shows stretched -exponential decay. These results shows the two factors viz, cooperative dynamics and rate of dynamics of spin, may be responsible for the low temperature magnetic-glassy behavior, concluded from bifurcation of zero field cooled (ZFC) and field cooled (FC) data of dc magnetization. Temperature dependent dielectric measurement shows a possible phase transition, seen in the dielectric-relaxation time and dielectric constant in the range 200 – 240K. Comparison of dielectric and magnetization data indicates a possibility of magneto-electric coupling.
Journal of Applied Physics, 2015
Dielectric and magnetodielectric measurements are done on BiFe1−xCoxO3: x = 0, 0.01, and 0.02 in ... more Dielectric and magnetodielectric measurements are done on BiFe1−xCoxO3: x = 0, 0.01, and 0.02 in the temperature range 70–300 K and up to magnetic field 1.3 T. The dielectric data are well described by Haverliak–Negami expression plus an additional term for the Maxwell Wagner (MW) type relaxations, whose contribution is dominant near room temperature. The parameters obtained from the fitting of data using the above mentioned expression, suggest slowing down of relaxation and approach towards ideal Debye type relaxations, as the temperature is lowered. The dielectric relaxations obey polaronic variable range hopping model with distinct activation energies (Ea) in the extrinsic (6.67T3/4 meV) and intrinsic (2.88T3/4 meV) regions for the parent sample (x = 0), and thus a distinct transition from extrinsic to intrinsic behavior is seen at 215 K while lowering the temperature. This distinct transition is missing for Co substituted samples probably due to the extrinsic region values of Ea...
Journal of Alloys and Compounds, 2015
Bi 13 Co 12)CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5)CoO 40 (BCFO) nanoparticles are prepared by sol... more Bi 13 Co 12)CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5)CoO 40 (BCFO) nanoparticles are prepared by sol-gel auto combustion method. The x-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100nm to 75nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30K, which seems to be competing paramagnetic and antiferromagnetic behaviour. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, throughout the temperature range for BCO. For BCFO, the behaviour may be divided under two regions viz., intrinsic (< 260K) and extrinsic (> 260K). Relaxation in both the regions is described by Arrhenius behaviour with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak-Negami equation is found to better describe the observed relaxation data. Highlights • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen.
Solid State Communications, 2015
Journal of Applied Physics, 2015
In the continuation of our previous work [Biswal et al., J. Appl. Phys. 115, 194106 (2014)] of bi... more In the continuation of our previous work [Biswal et al., J. Appl. Phys. 115, 194106 (2014)] of biphasic La2NiMnO6 (LNM) prepared via sol-gel technique, here we are reporting the effect of Cu substitution at Ni site of LNM. The powder x-ray diffraction results of La2Ni1−xCuxMnO6 (x = 0, 0.05, 0.1) confirm the biphasic nature (Pbnm + R-3c) for all samples along with increasing R-3c phase with Cu content in the sample. The temperature variation of magnetization (M) plot shows sharp ferromagnetic transitions of R-3c phase at 285 K, 278 K, and 270 K (obtained from dM/dT plot) and that of Pbnm phase at 165 K, 145 K, and 145 K for x = 0, 0.05, and 0.1, respectively. Weak antiferromagnetic type feature at 25 K (x = 0), is getting pronounced with Cu content in the sample and is now seen at 32 K & 266 K (for x = 0.05) and 32K & 257 K (for x = 0.1). Fitting of Curie-Weiss law in the paramagnetic region of χ−1 vs T plot results slightly lower values of corresponding Tc's of R-3 c phase (277...
Journal of Alloys and Compounds, 2015
Room temperature magnetoelectric (ME) measurements are carried out on phase pure BiFeO 3 and BiFe... more Room temperature magnetoelectric (ME) measurements are carried out on phase pure BiFeO 3 and BiFe 0.98 Co 0.02 O 3 , prepared via sol-gel technique. At zero magnetic field, the longitudinal ME coupling coefficient (α) for BiFeO 3 is found to be α = 20.935, which decreases on application of magnetic field and displays hysteresis in magnetic field (H) for the increasing and decreasing cycle of H. This hysteresis disappears for BiFe 0.98 Co 0.02 O 3 and α becomes linear in H along with 17% drop in the magnitude compared to parent BiFeO 3. In spite of 17% drop, magnitude of α = 17.375 is good enough for device applications especially where α must follow the applied magnetic field linearly, e.g., transistors, transducers, etc. Neutron diffraction studies show lattice stiffening due to cobalt substitution in BiFeO 3 and likely to be the cause of disappearance of hysteresis in α. Calculated value of polarization P (using the parameters derived from neutron diffraction) shows 19% drop in magnitude of P for cobalt substituted sample. Surprisingly, dielectric measurements also showed 18% decrease in dielectric constant ' ε due to cobalt doping. Such a one to one correspondence in the three parameters viz., α, P and ' ε , reflects a strong interdependence so that variation in any one of them is reciprocated in the other. Room temperature magnetodielectricity of 5% and 3.2% is observed for BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively. Interestingly similar to α, ߝ ᇱ also shows hysteresis in magnetic field for BiFeO 3 and the hysteresis disappears for BiFe 0.08 Co 0.02 O 3. The dc electrical resistivity measurements, suggests variable range hopping (VRH) with average hopping range 50.038 ܶ .ଶହ ⁄ and 40.058 ܶ .ଶହ ⁄ in BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively, as the conduction mechanism.
AIP Conference Proceedings, 2015
AIP Conference Proceedings, 2015
AIP Conference Proceedings, 2015
Journal of Applied Physics, 2012
The Bi2Sr2CaCu2O8/BiFeO3 (BSCCO/BFO) nano composite for various BFO weight percentage is prepared... more The Bi2Sr2CaCu2O8/BiFeO3 (BSCCO/BFO) nano composite for various BFO weight percentage is prepared and studied for electrical transport. Double resistive superconducting transition is seen in all composite samples with increasing semiconducting nature as a function of BFO content. Initially, the added BFO goes mainly to the grain boundary and from 10% onwards, it enters grains as well, acting as pinning centers. The conduction mechanism in BSCCO shows weak localization for low BFO, tunneling in intermediate BFO, and power law behavior (similar to metal-insulator boundary) for higher BFO samples. The paraconductivity studies reveal the 2D-3D transition in parent BSCCO and the composites, with a signature of percolative behavior in the composites. The study of critical current density reveals two types of Josephson junction in the composites: (1) thin intrinsic superconductor-insulator-superconductor (SIS) type present in all samples including parent BSCCO and (2) extrinsic type due to...
AIP Conference Proceedings, 2013
This thesis presents the study of structural, surface morphology, electric, magnetic, magnetoelec... more This thesis presents the study of structural, surface morphology, electric, magnetic, magnetoelectric and magnetodielectric properties of Cobalt substituted multiferroic BiFeO3. Since their discovery, multiferroics have brought tremendous interest among the researchers due to the coexistence of various ferroic order parameters. The synchronization of the magnetic and electric order parameter, hence generating magnetoelectric coupling, has been of importance in particular. Various functional devices aiming at the coupling between the ferroelectric and ferromagnetic order parameter are underway. Among all, the perovskite oxides (ABO3) based multiferroics are of prime interest due to their ease of synthesis and easy to understand physical interactions due to their simple structure. Bismuth Ferrite (BiFeO3), is a prototype ABO3 type multiferroic material, possessing the ferroelectric Curie temperature (Tc) ~ 1103K and antiferromagnetic Neel temperature (TN) ~ 643K. It exhibits a weak ne...
AIP Conference Proceedings, 2014
ABSTRACT Magnetic relaxation measurements at 5K, 50K and 120K on BiFeO 3 prepared by sol-gel auto... more ABSTRACT Magnetic relaxation measurements at 5K, 50K and 120K on BiFeO 3 prepared by sol-gel auto combustion method shows stretched -exponential decay. These results shows the two factors viz, cooperative dynamics and rate of dynamics of spin, may be responsible for the low temperature magnetic-glassy behavior, concluded from bifurcation of zero field cooled (ZFC) and field cooled (FC) data of dc magnetization. Temperature dependent dielectric measurement shows a possible phase transition, seen in the dielectric-relaxation time and dielectric constant in the range 200 – 240K. Comparison of dielectric and magnetization data indicates a possibility of magneto-electric coupling.