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sadaf jethva

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Kiran Dasari

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Gautam Anand

Indian Institute of Engineering Science and Technology, Shibpur

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Papers by sadaf jethva

Research paper thumbnail of Electronic Structure studies on Ca-doped BiFeO3 Multiferroic films using X-ray Absorption Spectroscopy

Introduction Multiferroic materials exhibit coexisting polar and magnetic orders have unique and ... more Introduction Multiferroic materials exhibit coexisting polar and magnetic orders have unique and interesting properties useful for various applications involving spintronic devices, storage devices, sensors, high-density memory and multi-state electronic devices, etc. [1]. Amongst various multiferroics studied till date, BiFeO3 (BFO) has emerged as the most promising candidate. Pure BFO is characterized by serious leakage problems arising due to the presence of small amount of Fe ions and oxygen vacancies [2], which makes it practically unusable. Several methods have been suggested to reduce the leakage current, such as, annealing of BFO films in oxygen environment and doping with rare earth and divalent ion [3]. Substitution on A site is more important as it reduces the number of Bi ions which further reduces the 6s lone pairs in the system. The present study on, the investigations of the electronic structure, dielectric and magnetic properties of Ca-doped BiFeO3 films is of major ...

Research paper thumbnail of Effect of La-substitution on magnetic properties of ErFeO3 orthoferrites

Journal of Magnetism and Magnetic Materials

Research paper thumbnail of Electronic structure correlation with ferroelectric behavior of Ca-doped BiFeO3 films

Journal of Electron Spectroscopy and Related Phenomena

Research paper thumbnail of Electronic excitation induced modifications in the ferroelectric polarization of BiFeO3 thin films

Research paper thumbnail of Studies on the structure and dielectric properties of Ca-doped BiFeO3 multiferroics

Research paper thumbnail of Effect of strain on the modifications in electronic structure and resistive switching in Ca-doped BiFeO3 films

Journal of Applied Physics

Research paper thumbnail of Structural, transport and magnetotransport properties of Ru-doped La 0.5 Sr 0.5 Mn 1−x Ru x O 3 (x = 0.0 & 0.05) manganite

Physica B: Condensed Matter

Research paper thumbnail of Impedance studies on Ca – doped BiFeO3 multiferroic: Role of grain and grain boundary

Research paper thumbnail of Magnetic structure and magnetism of divalent Zn doped NdMnO3

Research paper thumbnail of Modification in the dielectric behavior of cobalt doped ZnO synthesized by co-precipitation method

Research paper thumbnail of Structure & magnetic behavior of Cu doped NdMnO3 manganite

Research paper thumbnail of Grain boundary effects on the structural, microstructural and transport behavior of sol – gel grown PrMnO3 nanoparticles

Research paper thumbnail of Grain morphology dependent dielectric behaviour of ZnO – BaTiO3 composites

Research paper thumbnail of Resistive switching and magnetic behavior of Bi0.8Ba0.2FeO3 / SrRuO3 / SrTiO3films: role of thickness-dependent strain

Journal of Physics D: Applied Physics, 2016

Research paper thumbnail of Modifications in the electronic structure of Rare-Earth doped BiFeO3 multiferroic

Solid State Communications, 2015

Research paper thumbnail of Studies on electronic structure and dielectric properties of La-doped ErFeO3 orthoferrites

Journal of Alloys and Compounds

We report the results of the studies on crystal structure, electronic structure and dielectric pr... more We report the results of the studies on crystal structure, electronic structure and dielectric properties of Er 1-x La x FeO 3 (ELFO) (x ¼ 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) orthoferrites synthesized by co-precipitation method. Rietveld refinement of the XRD data confirms the orthorhombic crystal structure for all the samples. The study of Fe L 3,2-edge X-ray Absorption spectroscopy shows the presence of Fe-ions in 3 þ valence state in all the samples. Investigations on the dielectric behavior of ELFO samples over the wide frequency range of 20 Hz to 5 MHz show the increment in the dielectric constant with La-doping. ErFeO 3 has the lowest value of dielectric constant whereas LaFeO 3 has the highest value of dielectric constant among all the samples. Effect of grain and grain boundary contribution on the dielectric behavior is studied using complex dielectric permittivity. The observed colossal dielectric behavior in LaFeO 3 is attributed to the combined contribution from the intrinsic dielectric constant of the material and that due to the modification in the microstructure.

Research paper thumbnail of Doping induced modifications in the electronic structure and magnetism of ZnO films: Valence band and conduction band studies

a b s t r a c t The electronic structure of Pulsed Laser Deposited (PLD) ZnO, Zn 0.95 Fe 0.05 O (... more a b s t r a c t The electronic structure of Pulsed Laser Deposited (PLD) ZnO, Zn 0.95 Fe 0.05 O (ZFO), Zn 0.98 Al 0.02 O (ZAO) and Zn 0.93 Fe 0.05 Al 0.02 O (ZFAO) films were investigated by Photoelectron spectroscopy and X-ray absorption spectroscopy. X-ray diffraction and -scan measurements show epitaxial c-directional growth of the films. Temperature dependent magnetization and M-H loop measurements show the presence of room temperature magnetic ordering in all the films. Fittings of Fe 2p XPS and Fe L 3,2 −edge XAS of ZFO and ZFAO films show the presence of Fe, in both, Fe +2 and Fe +3 states in tetrahedral symmetry. Valence band spectra in resonance mode show resonance photon energy at 56 eV showing the presence of Fe 2+ state (∼2 eV) near the Fermi level. A significant effect of Fe and Al doping on the spectral shape of O K-edge XAS was observed. Results of the Spectroscopic studies reveal that, ferromagnetism in the films is due to the contribution of oxygen deficiency which increases the number of charge carriers that take part in the exchange interaction. Al co-doping with Fe (in ZFAO) results in the enhancement of saturation magnetization by increase in the carrier-mediated ferromagnetic exchange interaction.

Research paper thumbnail of Studies on structural, morphological and electroresistance properties of sol–gel grown nanostructured PrMnO3

We report the results of the studies on structural, microstructural and transport properties of n... more We report the results of the studies on structural, microstructural and transport properties of nanostructured PrMnO 3 (PMO) synthesized by acetate precursor based modified sol-gel route. Role of sintering temperature in the modifications in the physical properties of PMO samples has been studied. Structural analysis, using X-ray diffraction (XRD), reveals the single phasic nature of all the PMO samples, while analysis of TEM reveals the uniform sized distribution of nanoparticles, showing agglomeration effect in samples sintered at higher temperatures. SEM micrographs depict the increase in grain size with sharp boundaries in the samples sintered at higher temperatures. Sintering temperature and size dependent resistivity behavior under different applied electric fields has been understood in the context of grain size and boundary nature. PMO have also been studied for their electroresistance (ER) and electric pulse induced resistance (EPIR) change behavior which are highly useful features for spintronic based practical applications.

Research paper thumbnail of Electronic Structure studies on Ca-doped BiFeO3 Multiferroic films using X-ray Absorption Spectroscopy

Introduction Multiferroic materials exhibit coexisting polar and magnetic orders have unique and ... more Introduction Multiferroic materials exhibit coexisting polar and magnetic orders have unique and interesting properties useful for various applications involving spintronic devices, storage devices, sensors, high-density memory and multi-state electronic devices, etc. [1]. Amongst various multiferroics studied till date, BiFeO3 (BFO) has emerged as the most promising candidate. Pure BFO is characterized by serious leakage problems arising due to the presence of small amount of Fe ions and oxygen vacancies [2], which makes it practically unusable. Several methods have been suggested to reduce the leakage current, such as, annealing of BFO films in oxygen environment and doping with rare earth and divalent ion [3]. Substitution on A site is more important as it reduces the number of Bi ions which further reduces the 6s lone pairs in the system. The present study on, the investigations of the electronic structure, dielectric and magnetic properties of Ca-doped BiFeO3 films is of major ...

Research paper thumbnail of Effect of La-substitution on magnetic properties of ErFeO3 orthoferrites

Journal of Magnetism and Magnetic Materials

Research paper thumbnail of Electronic structure correlation with ferroelectric behavior of Ca-doped BiFeO3 films

Journal of Electron Spectroscopy and Related Phenomena

Research paper thumbnail of Electronic excitation induced modifications in the ferroelectric polarization of BiFeO3 thin films

Research paper thumbnail of Studies on the structure and dielectric properties of Ca-doped BiFeO3 multiferroics

Research paper thumbnail of Effect of strain on the modifications in electronic structure and resistive switching in Ca-doped BiFeO3 films

Journal of Applied Physics

Research paper thumbnail of Structural, transport and magnetotransport properties of Ru-doped La 0.5 Sr 0.5 Mn 1−x Ru x O 3 (x = 0.0 & 0.05) manganite

Physica B: Condensed Matter

Research paper thumbnail of Impedance studies on Ca – doped BiFeO3 multiferroic: Role of grain and grain boundary

Research paper thumbnail of Magnetic structure and magnetism of divalent Zn doped NdMnO3

Research paper thumbnail of Modification in the dielectric behavior of cobalt doped ZnO synthesized by co-precipitation method

Research paper thumbnail of Structure & magnetic behavior of Cu doped NdMnO3 manganite

Research paper thumbnail of Grain boundary effects on the structural, microstructural and transport behavior of sol – gel grown PrMnO3 nanoparticles

Research paper thumbnail of Grain morphology dependent dielectric behaviour of ZnO – BaTiO3 composites

Research paper thumbnail of Resistive switching and magnetic behavior of Bi0.8Ba0.2FeO3 / SrRuO3 / SrTiO3films: role of thickness-dependent strain

Journal of Physics D: Applied Physics, 2016

Research paper thumbnail of Modifications in the electronic structure of Rare-Earth doped BiFeO3 multiferroic

Solid State Communications, 2015

Research paper thumbnail of Studies on electronic structure and dielectric properties of La-doped ErFeO3 orthoferrites

Journal of Alloys and Compounds

We report the results of the studies on crystal structure, electronic structure and dielectric pr... more We report the results of the studies on crystal structure, electronic structure and dielectric properties of Er 1-x La x FeO 3 (ELFO) (x ¼ 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) orthoferrites synthesized by co-precipitation method. Rietveld refinement of the XRD data confirms the orthorhombic crystal structure for all the samples. The study of Fe L 3,2-edge X-ray Absorption spectroscopy shows the presence of Fe-ions in 3 þ valence state in all the samples. Investigations on the dielectric behavior of ELFO samples over the wide frequency range of 20 Hz to 5 MHz show the increment in the dielectric constant with La-doping. ErFeO 3 has the lowest value of dielectric constant whereas LaFeO 3 has the highest value of dielectric constant among all the samples. Effect of grain and grain boundary contribution on the dielectric behavior is studied using complex dielectric permittivity. The observed colossal dielectric behavior in LaFeO 3 is attributed to the combined contribution from the intrinsic dielectric constant of the material and that due to the modification in the microstructure.

Research paper thumbnail of Doping induced modifications in the electronic structure and magnetism of ZnO films: Valence band and conduction band studies

a b s t r a c t The electronic structure of Pulsed Laser Deposited (PLD) ZnO, Zn 0.95 Fe 0.05 O (... more a b s t r a c t The electronic structure of Pulsed Laser Deposited (PLD) ZnO, Zn 0.95 Fe 0.05 O (ZFO), Zn 0.98 Al 0.02 O (ZAO) and Zn 0.93 Fe 0.05 Al 0.02 O (ZFAO) films were investigated by Photoelectron spectroscopy and X-ray absorption spectroscopy. X-ray diffraction and -scan measurements show epitaxial c-directional growth of the films. Temperature dependent magnetization and M-H loop measurements show the presence of room temperature magnetic ordering in all the films. Fittings of Fe 2p XPS and Fe L 3,2 −edge XAS of ZFO and ZFAO films show the presence of Fe, in both, Fe +2 and Fe +3 states in tetrahedral symmetry. Valence band spectra in resonance mode show resonance photon energy at 56 eV showing the presence of Fe 2+ state (∼2 eV) near the Fermi level. A significant effect of Fe and Al doping on the spectral shape of O K-edge XAS was observed. Results of the Spectroscopic studies reveal that, ferromagnetism in the films is due to the contribution of oxygen deficiency which increases the number of charge carriers that take part in the exchange interaction. Al co-doping with Fe (in ZFAO) results in the enhancement of saturation magnetization by increase in the carrier-mediated ferromagnetic exchange interaction.

Research paper thumbnail of Studies on structural, morphological and electroresistance properties of sol–gel grown nanostructured PrMnO3

We report the results of the studies on structural, microstructural and transport properties of n... more We report the results of the studies on structural, microstructural and transport properties of nanostructured PrMnO 3 (PMO) synthesized by acetate precursor based modified sol-gel route. Role of sintering temperature in the modifications in the physical properties of PMO samples has been studied. Structural analysis, using X-ray diffraction (XRD), reveals the single phasic nature of all the PMO samples, while analysis of TEM reveals the uniform sized distribution of nanoparticles, showing agglomeration effect in samples sintered at higher temperatures. SEM micrographs depict the increase in grain size with sharp boundaries in the samples sintered at higher temperatures. Sintering temperature and size dependent resistivity behavior under different applied electric fields has been understood in the context of grain size and boundary nature. PMO have also been studied for their electroresistance (ER) and electric pulse induced resistance (EPIR) change behavior which are highly useful features for spintronic based practical applications.

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