Rujuta Doshi | Indian Institute of Science (original) (raw)
Papers by Rujuta Doshi
When referring to this work, full bibliographic details including the author, title, awarding ins... more When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given.
Physica B: Condensed Matter, 2015
In this communication, we report the results of the studies on structural, microstructural, trans... more In this communication, we report the results of the studies on structural, microstructural, transport and magnetotransport behavior of La 0.8 À x Pr 0.2 Sr x MnO 3 (LPSMO) (x ¼ 0.1, 0.2 and 0.3) manganite films grown on (100) single crystalline SrTiO 3 (STO) substrate using low cost chemical solution deposition (CSD) method. Films with similar compositions were also grown using sophisticated pulsed laser deposition (PLD) technique and results of structural and transport studies obtained for CSD grown films were compared with PLD grown films. Structural studies show that all the CSD and PLD grown films possess single crystalline nature with compressive and tensile strain, respectively. Surface morphology, studied using atomic force microscope (AFM), reveals the island like grain morphology in CSD grown films while PLD grown films possess smooth film surfaces. Carrier density dependent transport properties of the films have been discussed in the context of zener double exchange (ZDE) mechanism. Lower resistivity and higher transition temperature (T P) observed in CSD grown films as compared to PLD grown films have been discussed in the light of structural strain and surface morphology of the films. Various models and mechanisms have been employed to understand the charge transport in CSD and PLD grown films. Also, observation of low temperature resistivity minima behavior in all the CSD and PLD grown LPSMO films has been explained in the context of electron-electron scattering mechanism.
ABSTRACT Nanophasic samples of La 0.7 Pb 0.3 MnO 3 (LPMO) manganites were prepared by sol-gel met... more ABSTRACT Nanophasic samples of La 0.7 Pb 0.3 MnO 3 (LPMO) manganites were prepared by sol-gel method. The samples were sintered at different temperatures ranging from 950 to 1150°C. It is shown that the transport and magnetoresistive properties of LPMO samples strongly depend on the sintering temperature (Ts). Microstructural studies show secondary grain growth which influences the transport and magnetotransport properties of the LPMO polycrystalline samples. In this communication, we report the effect of sintering temperature on the occurrence of secondary grain growth in sol-gel synthesized nanostructured LPMO samples. It is observed that, this growth improves the extrinsic MR below I-M transition. The microstructural studies using AFM shows the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D -1) modifying the properties of LPMO samples.
ABSTRACT In this communication, we report the effect of grain growth modifications on the transpo... more ABSTRACT In this communication, we report the effect of grain growth modifications on the transport and magnetotransport of Sol-Gel grown polycrystalline La 0.7 Pb 0.3 MnO 3 (LPMO) manganites sintered at various temperatures. The structural studies using Rietveld refinement of the XRD data confirms single phasic nature of the samples while the AFM investigations show the development of secondary grains in the sample sintered at 1000 o C. The effect of secondary grains on the transport and magnetotransport properties becomes prominent in the samples sintered at 1050 o C and above. The temperature dependent MR behavior of all the LPMO samples sintered at various temperatures has been understood in the light of modifications in their microstructural properties. Introduction The observation of anomalously high magnetoresistance (MR) in the La 1-x A x MnO 3 (A = Ca, Sr, Ba or Pb) manganites has spurred the renewed interest in undertaking the systematic investigations on these materials [1, 2]. The studies on mixed valent manganites are important from fundamental understanding of the charge transport mechanisms as well as from the point of view of their potential usefulness in field and temperature sensor application. Lead doped manganites in polycrystalline bulk and single crystalline thin film forms have been studied owing to their high insulator -metal transition temperature (T P above 330K) and long range spin ordering exhibited by them [3, 4]. Although, the colossal magnetoresistance (CMR) behavior exhibited by manganites has been explained satisfactorily and various device applications of these materials have been successfully shown to exist, however, the necessity of large applied high field to produce large intrinsic MR based on Zener Double exchange mechanism at T P or curie temperature, T C , has prompted the researchers to synthesize newer doped manganites having large MR at high temperatures under low applied fields. It is reported that, grain boundary effects contribute effectively in the intrinsic MR behavior [5, 6]. However, it has been found that the local disruption of the magnetic order leads to the modification in electrical conduction due to the structural defects and grain boundary effects. The MR behavior arising due to these external factors is termed as extrinsic MR [7]. This kind of MR is also called as low field MR (LFMR) or grain boundary MR (GBMR) which is controlled by the external parameter, grain boundaries hence termed as external MR [8]. In this communication, we report the results of the structural studies carried out using analysis of the XRD data obtained on LPMO samples. Also, the microstructural investigations carried out on various LPMO samples sintered at different temperatures (TS) have been understood in the context of grain growth dependent modifications of the transport and magnetotransport behavior of samples.
ABSTRACT The Studies on La 0.7 Pb 0.3 MnO 3 (LPMO) manganite thin films grown on single crystalli... more ABSTRACT The Studies on La 0.7 Pb 0.3 MnO 3 (LPMO) manganite thin films grown on single crystalline LAO [100] substrate using the cost effective Sol-Gel (Spin Coating) technique shows that, the microstructural properties depend on the film thickness. It is observed that, the film-substrate interface and surface properties strongly affect the electrical transport and magnetotransport of the film. The films with thickness > 100nm exhibit better transport with the reduction in structural strain at the interface which enhances the transfer of e g electrons and hence increase in insulator -metal transition temperature (T P).
ABSTRACT The effect of sintering temperature on the transport and magnetotransport of bulk nanost... more ABSTRACT The effect of sintering temperature on the transport and magnetotransport of bulk nanostructured La 0.7 Ca 0.3 MnO 3 (LCMO) manganites synthesized using sol-gel technique has been investigated. The modifications in the properties of LCMO manganites as a function of sintering temperature have been understood in terms of the changes in Mn-O-Mn bond angles and Mn-O bond lengths. Microstructure dependent transport behavior of the LCMO studied is reflected in the variation of low temperature magnetoresistance (MR) with sintering temperature.
ABSTRACT The structure-magnetic property dependence in 5 and 15% Co-doped ZnO samples synthesized... more ABSTRACT The structure-magnetic property dependence in 5 and 15% Co-doped ZnO samples synthesized using Solid State Reaction (SSR) and Sol-Gel routes has been investigated using XRD, SEM and magnetization measurements. Rietveld refinement of the XRD data confirms the single phasic hexagonal wurtzite structure of the samples. The microstructure is found to depend strongly on the synthesis route and temperature history. The Sol-Gel grown 5% Co-doped ZnO sample exhibit weak ferromagnetic (FM) behaviour. The Sol-Gel grown samples exhibit pronounced magnetic susceptibility and magnetization values as compared to samples synthesized by SSR method. The possible role of grain morphology in attributing the FM in Sol-Gel grown Co-doped ZnO samples has been discussed.
ABSTRACT We report the temperature dependent I-V characteristics of the 200nm La 0.5 Pr 0.2 Sr 0.... more ABSTRACT We report the temperature dependent I-V characteristics of the 200nm La 0.5 Pr 0.2 Sr 0.3 MnO 3 (LPSMO) / SrNb 0.2 Ti 0.8 O 3 (SNTO) bi-layered p-n junction diode fabricated using Pulsed Laser Deposition (PLD) technique. The device exhibits good rectifying behavior at all the temperatures in the range 5-250K. The saturation voltage (V C) decreases with increase in temperature which can be understood on the basis of modifications in the energy gap between e g bands with temperature.
![Research paper thumbnail of Temperature Dependent Switching of Magnetoresistance in Trilayered ZnO∕La[sub 0.7]Sr[sub 0.3]MnO[sub 3]∕SrNb[sub 0.2]Ti[sub 0.8]O[sub 3] Device](https://attachments.academia-assets.com/93600731/thumbnails/1.jpg)
](AIP Conference Proceedings, 2011
Numerical simulation of spall in lead accounting for its occurrence in solid as well as liquid ph... more Numerical simulation of spall in lead accounting for its occurrence in solid as well as liquid phases
International Journal of Modern Physics B, 2012
We report the modifications in the transport and magnetotransport in La 0.7 Ca 0.3 Mn 1-x Al x O ... more We report the modifications in the transport and magnetotransport in La 0.7 Ca 0.3 Mn 1-x Al x O 3 (LCMAO); x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 polycrystalline manganites synthesized by conventional ceramic method. XRD studies reveal the single phasic orthorhombic structure for all the Al -doped LCMO samples without any detectable impurities and structural phase transition. SEM micrographs show island-like grain growth in all the samples studied. Transport measurements indicate an increase in resistivity and decrease in metal-insulator (M-I) transition temperature (TP) with the increase in Al -concentration. Field and temperature dependent variation in MR for all the Al (x) doped LCMO samples has been discussed in detail in the light of substitution induced structural disorder.
Physica B: Condensed Matter, 2011
Effect of A-site disorder in half-doped La 0.5 Ca 0.5 MnO 3 created by the substitution of Tb at ... more Effect of A-site disorder in half-doped La 0.5 Ca 0.5 MnO 3 created by the substitution of Tb at La site is studied through temperature dependent neutron diffraction, resistivity, and magnetization on La 0.375 Tb 0.125 Ca 0.5 MnO 3 (LTC) to identify the evolution of phases as a function of temperature and magnetic field. Contrary to the parent system,
Physica B: Condensed Matter, 2011
... Doshi, CM Thaker, Swati Pandya, V. Ganesan and DG Kuberkar, J. Nanosci. Nanotechnol. 9 (2009)... more ... Doshi, CM Thaker, Swati Pandya, V. Ganesan and DG Kuberkar, J. Nanosci. Nanotechnol. 9 (2009) 5681-5686. 5 [5] JZ Liu, IC Chang, S. Irons, P. Klavins, RN Shelton, K. Song and SR Wasserman, Appl. Phys. Lett. 66 (1995) 3218-3220. [6] SS Manoharan, NY Vasanthacharya ...
Physica B: Condensed Matter, 2011
... range is due to spin flip scattering at various interfaces which suppresses net spin polariza... more ... range is due to spin flip scattering at various interfaces which suppresses net spin polarization of ... The experimental facilities provided by Dr. R. Rawat and Dr. V. Ganesan, UGC-DAE CSR ... PSS is thankful to CSIR, New Delhi for the award of Senior Research Fellowship (No. ...
Materials Research Bulletin, 2011
Materials Research Bulletin, 2011
Journal of Nanoscience and Nanotechnology, 2009
Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a ... more Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a good control over the stoichiometry and morphology which helps to tailor the required materials on atomic scale to suit specific applications. Nanophasic polycrystalline samples of La 0 7 Pb 0 3 MnO 3 (LPMO) manganites having perovskite type structure synthesized by novel Sol-Gel technique using acetate precursor route were sintered at various temperatures in the range 950-1150 C for studying the effect of grain size modifications on their structural, transport and magnetotransport properties. X-ray diffraction (XRD) studies show that the samples exhibit rhombohedral structure crystallizing in space group R-3C. Microstructural investigations using Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) measurements reveal the observation of secondary grain growth behavior starting in the sample sintered at 1000 C. The d.c. four probe resistivity measurements with and without applied magnetic field in the temperature range of 2-380 K, show the effect of secondary grain growth on the magnetoresistance (MR) behavior of LPMO manganites. The microstructural studies show the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D −1) which in turn modifies the physical properties of samples under investigation. All the samples exhibit resistivity minima at ∼30 K which can be explained in terms of e-e interaction at 0 Tesla field. There is a correlation between the parameters derived from e-e scattering model and the secondary grain growth present in the samples. The results of the microstructural and MR measurements on the nanostructured LPMO manganites have been discussed in detail.
Journal of Nanoscience and Nanotechnology, 2008
Grain-size dependence of electronic transport and magnetoresistance (MR) properties of nanostruct... more Grain-size dependence of electronic transport and magnetoresistance (MR) properties of nanostructured La0.7Sr0.3 MnO3 (LSMO) manganite thin films on LaAlO3 (100) single crystal substrates prepared using Chemical Solution Deposition (CSD) technique have been studied. The LSMO thin films were annealed at temperatures in the range of 700–1000 °C for different time intervals [6 h and 12 h] and crystallized as singlephase LSMO. Microstructural studies carried out using AFM show a marginal increase in the grain-size from 50 to 90 nm as the temperature was varied from 700 °C to 1000 °C respectively. It has been observed that the insulator-metal transition (TP) and MR depend on the grain size. In zero applied field, resistivity reduction is ∼ 103 at 5 K for the films annealed at 700 °C [TP ∼ 341 K] and 1000 °C [TP ∼ 373 K]. MR versus H isotherms reveal that MR enhances in the vicinity of TP but decreases at low temperatures. The results obtained from the electronic and magnetotransport stud...
Journal of Materials Research, 2010
The structural, transport, and magnetotransport properties of single-phase, homogeneous nanostruc... more The structural, transport, and magnetotransport properties of single-phase, homogeneous nanostructured La0.7Sr0.3MnO3 (LSMO) manganites synthesized by the coprecipitation route were investigated and the effect of sintering temperature on the microstructure of LSMO compounds was studied. A strong dependence of transport and magnetotransport behavior on the microstructure and nature of grain boundaries has been observed in the single-phase LSMO sintered at various temperatures. High-field magnetoresistance (HFMR) at room temperature is found to increase [13% (LS6) to 25% (LS9)] while low temperature (5 K) magnetoresistance decreases [75% (LS6) to 46% (LS9)] under 9 T field with increase in sintering temperature, which has been attributed to the spin-polarized tunneling and spin-dependent scattering of charge carriers.
Journal of Magnetism and Magnetic Materials, 2009
We report the results of the temperature-dependent neutron diffraction measurements on the nearly... more We report the results of the temperature-dependent neutron diffraction measurements on the nearly half-doped (La 0.325 Tb 0.125)(Ca 0.3 Sr 0.25)MnO 3 manganite sample. The simultaneous doping of magnetic Tb 3+ and divalent Sr 2+ in the La 0.7 Ca 0.3 MnO 3 system results into a large A-site size disorder. Rietveld refinement of neutron diffraction data reveal that the single phase sample crystallizes in a distorted orthorhombic structure. Increased /r A S value affects the transport behavior that results into an insulating-like behavior of the sample. Under application of 1 T field sample exhibit insulating-like behavior while insulator-metal transition (T IM) is exhibited under 5 and 8 T fields. Variable range hoping (VRH) mechanism of charge carriers is exhibited in the insulating region. Field cooled and zero field cooled magnetization measurement shows the Curie temperature (T C)$47 K. The refinement of the ND data collected at various temperatures below 300 K shows that there is no structural phase transition in the compound. Around 100 K, a magnetic peak appears at lower angle that can be ascribed to the presence of the A-type antiferromagnetic (AFM) phase. Two more peaks are observed around 50 K at lower angles that can be fitted in CE-type antiferromagnetic phase. Splitting of the peaks at lower temperatures is the signature of orbital ordering in the presently studied nearly half-doped manganite system. Results of the detailed structural analysis of the temperature-dependent ND measurements on (LaTb) 0.45 (CaSr) 0.55 MnO 3 sample has been discussed in the light of coexisting A-type and CE-type antiferromagnetic phases present in the sample at low temperature.
Applied Surface Science, 2012
Nanostructured polycrystalline La 0.7 Ca 0.3 MnO 3 (LCMO) and Nd 0.7 Sr 0.3 MnO 3 (NSMO) manganit... more Nanostructured polycrystalline La 0.7 Ca 0.3 MnO 3 (LCMO) and Nd 0.7 Sr 0.3 MnO 3 (NSMO) manganites have been successfully synthesized at various temperatures ranging between 700 and 1100 • C using Sol-Gel method. Crystalline nature and morphology of the samples have been studied using XRD (Rietveld analysis) and TEM measurements. SEM studies reveal nanostructured grain morphology of LCMO and NSMO samples. It is observed that, with increase in sintering temperature, crystallinity and grain morphology get improved resulting in better transport. A strong dependence of transport on size variance has been observed in the systems studied. The modified transport and better magnetotransport properties of the manganites have been observed due to the large surface to volume ratio (surface contribution) in the nanostructured manganites. The observation of large low temperature MR in both the manganite systems and the interplay between the intrinsic and extrinsic MR components has been explained in the light of spin polarized tunneling effect, grain morphology, grain boundary nature and size disorder effect.
When referring to this work, full bibliographic details including the author, title, awarding ins... more When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given.
Physica B: Condensed Matter, 2015
In this communication, we report the results of the studies on structural, microstructural, trans... more In this communication, we report the results of the studies on structural, microstructural, transport and magnetotransport behavior of La 0.8 À x Pr 0.2 Sr x MnO 3 (LPSMO) (x ¼ 0.1, 0.2 and 0.3) manganite films grown on (100) single crystalline SrTiO 3 (STO) substrate using low cost chemical solution deposition (CSD) method. Films with similar compositions were also grown using sophisticated pulsed laser deposition (PLD) technique and results of structural and transport studies obtained for CSD grown films were compared with PLD grown films. Structural studies show that all the CSD and PLD grown films possess single crystalline nature with compressive and tensile strain, respectively. Surface morphology, studied using atomic force microscope (AFM), reveals the island like grain morphology in CSD grown films while PLD grown films possess smooth film surfaces. Carrier density dependent transport properties of the films have been discussed in the context of zener double exchange (ZDE) mechanism. Lower resistivity and higher transition temperature (T P) observed in CSD grown films as compared to PLD grown films have been discussed in the light of structural strain and surface morphology of the films. Various models and mechanisms have been employed to understand the charge transport in CSD and PLD grown films. Also, observation of low temperature resistivity minima behavior in all the CSD and PLD grown LPSMO films has been explained in the context of electron-electron scattering mechanism.
ABSTRACT Nanophasic samples of La 0.7 Pb 0.3 MnO 3 (LPMO) manganites were prepared by sol-gel met... more ABSTRACT Nanophasic samples of La 0.7 Pb 0.3 MnO 3 (LPMO) manganites were prepared by sol-gel method. The samples were sintered at different temperatures ranging from 950 to 1150°C. It is shown that the transport and magnetoresistive properties of LPMO samples strongly depend on the sintering temperature (Ts). Microstructural studies show secondary grain growth which influences the transport and magnetotransport properties of the LPMO polycrystalline samples. In this communication, we report the effect of sintering temperature on the occurrence of secondary grain growth in sol-gel synthesized nanostructured LPMO samples. It is observed that, this growth improves the extrinsic MR below I-M transition. The microstructural studies using AFM shows the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D -1) modifying the properties of LPMO samples.
ABSTRACT In this communication, we report the effect of grain growth modifications on the transpo... more ABSTRACT In this communication, we report the effect of grain growth modifications on the transport and magnetotransport of Sol-Gel grown polycrystalline La 0.7 Pb 0.3 MnO 3 (LPMO) manganites sintered at various temperatures. The structural studies using Rietveld refinement of the XRD data confirms single phasic nature of the samples while the AFM investigations show the development of secondary grains in the sample sintered at 1000 o C. The effect of secondary grains on the transport and magnetotransport properties becomes prominent in the samples sintered at 1050 o C and above. The temperature dependent MR behavior of all the LPMO samples sintered at various temperatures has been understood in the light of modifications in their microstructural properties. Introduction The observation of anomalously high magnetoresistance (MR) in the La 1-x A x MnO 3 (A = Ca, Sr, Ba or Pb) manganites has spurred the renewed interest in undertaking the systematic investigations on these materials [1, 2]. The studies on mixed valent manganites are important from fundamental understanding of the charge transport mechanisms as well as from the point of view of their potential usefulness in field and temperature sensor application. Lead doped manganites in polycrystalline bulk and single crystalline thin film forms have been studied owing to their high insulator -metal transition temperature (T P above 330K) and long range spin ordering exhibited by them [3, 4]. Although, the colossal magnetoresistance (CMR) behavior exhibited by manganites has been explained satisfactorily and various device applications of these materials have been successfully shown to exist, however, the necessity of large applied high field to produce large intrinsic MR based on Zener Double exchange mechanism at T P or curie temperature, T C , has prompted the researchers to synthesize newer doped manganites having large MR at high temperatures under low applied fields. It is reported that, grain boundary effects contribute effectively in the intrinsic MR behavior [5, 6]. However, it has been found that the local disruption of the magnetic order leads to the modification in electrical conduction due to the structural defects and grain boundary effects. The MR behavior arising due to these external factors is termed as extrinsic MR [7]. This kind of MR is also called as low field MR (LFMR) or grain boundary MR (GBMR) which is controlled by the external parameter, grain boundaries hence termed as external MR [8]. In this communication, we report the results of the structural studies carried out using analysis of the XRD data obtained on LPMO samples. Also, the microstructural investigations carried out on various LPMO samples sintered at different temperatures (TS) have been understood in the context of grain growth dependent modifications of the transport and magnetotransport behavior of samples.
ABSTRACT The Studies on La 0.7 Pb 0.3 MnO 3 (LPMO) manganite thin films grown on single crystalli... more ABSTRACT The Studies on La 0.7 Pb 0.3 MnO 3 (LPMO) manganite thin films grown on single crystalline LAO [100] substrate using the cost effective Sol-Gel (Spin Coating) technique shows that, the microstructural properties depend on the film thickness. It is observed that, the film-substrate interface and surface properties strongly affect the electrical transport and magnetotransport of the film. The films with thickness > 100nm exhibit better transport with the reduction in structural strain at the interface which enhances the transfer of e g electrons and hence increase in insulator -metal transition temperature (T P).
ABSTRACT The effect of sintering temperature on the transport and magnetotransport of bulk nanost... more ABSTRACT The effect of sintering temperature on the transport and magnetotransport of bulk nanostructured La 0.7 Ca 0.3 MnO 3 (LCMO) manganites synthesized using sol-gel technique has been investigated. The modifications in the properties of LCMO manganites as a function of sintering temperature have been understood in terms of the changes in Mn-O-Mn bond angles and Mn-O bond lengths. Microstructure dependent transport behavior of the LCMO studied is reflected in the variation of low temperature magnetoresistance (MR) with sintering temperature.
ABSTRACT The structure-magnetic property dependence in 5 and 15% Co-doped ZnO samples synthesized... more ABSTRACT The structure-magnetic property dependence in 5 and 15% Co-doped ZnO samples synthesized using Solid State Reaction (SSR) and Sol-Gel routes has been investigated using XRD, SEM and magnetization measurements. Rietveld refinement of the XRD data confirms the single phasic hexagonal wurtzite structure of the samples. The microstructure is found to depend strongly on the synthesis route and temperature history. The Sol-Gel grown 5% Co-doped ZnO sample exhibit weak ferromagnetic (FM) behaviour. The Sol-Gel grown samples exhibit pronounced magnetic susceptibility and magnetization values as compared to samples synthesized by SSR method. The possible role of grain morphology in attributing the FM in Sol-Gel grown Co-doped ZnO samples has been discussed.
ABSTRACT We report the temperature dependent I-V characteristics of the 200nm La 0.5 Pr 0.2 Sr 0.... more ABSTRACT We report the temperature dependent I-V characteristics of the 200nm La 0.5 Pr 0.2 Sr 0.3 MnO 3 (LPSMO) / SrNb 0.2 Ti 0.8 O 3 (SNTO) bi-layered p-n junction diode fabricated using Pulsed Laser Deposition (PLD) technique. The device exhibits good rectifying behavior at all the temperatures in the range 5-250K. The saturation voltage (V C) decreases with increase in temperature which can be understood on the basis of modifications in the energy gap between e g bands with temperature.
AIP Conference Proceedings, 2011
Numerical simulation of spall in lead accounting for its occurrence in solid as well as liquid ph... more Numerical simulation of spall in lead accounting for its occurrence in solid as well as liquid phases
International Journal of Modern Physics B, 2012
We report the modifications in the transport and magnetotransport in La 0.7 Ca 0.3 Mn 1-x Al x O ... more We report the modifications in the transport and magnetotransport in La 0.7 Ca 0.3 Mn 1-x Al x O 3 (LCMAO); x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 polycrystalline manganites synthesized by conventional ceramic method. XRD studies reveal the single phasic orthorhombic structure for all the Al -doped LCMO samples without any detectable impurities and structural phase transition. SEM micrographs show island-like grain growth in all the samples studied. Transport measurements indicate an increase in resistivity and decrease in metal-insulator (M-I) transition temperature (TP) with the increase in Al -concentration. Field and temperature dependent variation in MR for all the Al (x) doped LCMO samples has been discussed in detail in the light of substitution induced structural disorder.
Physica B: Condensed Matter, 2011
Effect of A-site disorder in half-doped La 0.5 Ca 0.5 MnO 3 created by the substitution of Tb at ... more Effect of A-site disorder in half-doped La 0.5 Ca 0.5 MnO 3 created by the substitution of Tb at La site is studied through temperature dependent neutron diffraction, resistivity, and magnetization on La 0.375 Tb 0.125 Ca 0.5 MnO 3 (LTC) to identify the evolution of phases as a function of temperature and magnetic field. Contrary to the parent system,
Physica B: Condensed Matter, 2011
... Doshi, CM Thaker, Swati Pandya, V. Ganesan and DG Kuberkar, J. Nanosci. Nanotechnol. 9 (2009)... more ... Doshi, CM Thaker, Swati Pandya, V. Ganesan and DG Kuberkar, J. Nanosci. Nanotechnol. 9 (2009) 5681-5686. 5 [5] JZ Liu, IC Chang, S. Irons, P. Klavins, RN Shelton, K. Song and SR Wasserman, Appl. Phys. Lett. 66 (1995) 3218-3220. [6] SS Manoharan, NY Vasanthacharya ...
Physica B: Condensed Matter, 2011
... range is due to spin flip scattering at various interfaces which suppresses net spin polariza... more ... range is due to spin flip scattering at various interfaces which suppresses net spin polarization of ... The experimental facilities provided by Dr. R. Rawat and Dr. V. Ganesan, UGC-DAE CSR ... PSS is thankful to CSIR, New Delhi for the award of Senior Research Fellowship (No. ...
Materials Research Bulletin, 2011
Materials Research Bulletin, 2011
Journal of Nanoscience and Nanotechnology, 2009
Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a ... more Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a good control over the stoichiometry and morphology which helps to tailor the required materials on atomic scale to suit specific applications. Nanophasic polycrystalline samples of La 0 7 Pb 0 3 MnO 3 (LPMO) manganites having perovskite type structure synthesized by novel Sol-Gel technique using acetate precursor route were sintered at various temperatures in the range 950-1150 C for studying the effect of grain size modifications on their structural, transport and magnetotransport properties. X-ray diffraction (XRD) studies show that the samples exhibit rhombohedral structure crystallizing in space group R-3C. Microstructural investigations using Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) measurements reveal the observation of secondary grain growth behavior starting in the sample sintered at 1000 C. The d.c. four probe resistivity measurements with and without applied magnetic field in the temperature range of 2-380 K, show the effect of secondary grain growth on the magnetoresistance (MR) behavior of LPMO manganites. The microstructural studies show the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D −1) which in turn modifies the physical properties of samples under investigation. All the samples exhibit resistivity minima at ∼30 K which can be explained in terms of e-e interaction at 0 Tesla field. There is a correlation between the parameters derived from e-e scattering model and the secondary grain growth present in the samples. The results of the microstructural and MR measurements on the nanostructured LPMO manganites have been discussed in detail.
Journal of Nanoscience and Nanotechnology, 2008
Grain-size dependence of electronic transport and magnetoresistance (MR) properties of nanostruct... more Grain-size dependence of electronic transport and magnetoresistance (MR) properties of nanostructured La0.7Sr0.3 MnO3 (LSMO) manganite thin films on LaAlO3 (100) single crystal substrates prepared using Chemical Solution Deposition (CSD) technique have been studied. The LSMO thin films were annealed at temperatures in the range of 700–1000 °C for different time intervals [6 h and 12 h] and crystallized as singlephase LSMO. Microstructural studies carried out using AFM show a marginal increase in the grain-size from 50 to 90 nm as the temperature was varied from 700 °C to 1000 °C respectively. It has been observed that the insulator-metal transition (TP) and MR depend on the grain size. In zero applied field, resistivity reduction is ∼ 103 at 5 K for the films annealed at 700 °C [TP ∼ 341 K] and 1000 °C [TP ∼ 373 K]. MR versus H isotherms reveal that MR enhances in the vicinity of TP but decreases at low temperatures. The results obtained from the electronic and magnetotransport stud...
Journal of Materials Research, 2010
The structural, transport, and magnetotransport properties of single-phase, homogeneous nanostruc... more The structural, transport, and magnetotransport properties of single-phase, homogeneous nanostructured La0.7Sr0.3MnO3 (LSMO) manganites synthesized by the coprecipitation route were investigated and the effect of sintering temperature on the microstructure of LSMO compounds was studied. A strong dependence of transport and magnetotransport behavior on the microstructure and nature of grain boundaries has been observed in the single-phase LSMO sintered at various temperatures. High-field magnetoresistance (HFMR) at room temperature is found to increase [13% (LS6) to 25% (LS9)] while low temperature (5 K) magnetoresistance decreases [75% (LS6) to 46% (LS9)] under 9 T field with increase in sintering temperature, which has been attributed to the spin-polarized tunneling and spin-dependent scattering of charge carriers.
Journal of Magnetism and Magnetic Materials, 2009
We report the results of the temperature-dependent neutron diffraction measurements on the nearly... more We report the results of the temperature-dependent neutron diffraction measurements on the nearly half-doped (La 0.325 Tb 0.125)(Ca 0.3 Sr 0.25)MnO 3 manganite sample. The simultaneous doping of magnetic Tb 3+ and divalent Sr 2+ in the La 0.7 Ca 0.3 MnO 3 system results into a large A-site size disorder. Rietveld refinement of neutron diffraction data reveal that the single phase sample crystallizes in a distorted orthorhombic structure. Increased /r A S value affects the transport behavior that results into an insulating-like behavior of the sample. Under application of 1 T field sample exhibit insulating-like behavior while insulator-metal transition (T IM) is exhibited under 5 and 8 T fields. Variable range hoping (VRH) mechanism of charge carriers is exhibited in the insulating region. Field cooled and zero field cooled magnetization measurement shows the Curie temperature (T C)$47 K. The refinement of the ND data collected at various temperatures below 300 K shows that there is no structural phase transition in the compound. Around 100 K, a magnetic peak appears at lower angle that can be ascribed to the presence of the A-type antiferromagnetic (AFM) phase. Two more peaks are observed around 50 K at lower angles that can be fitted in CE-type antiferromagnetic phase. Splitting of the peaks at lower temperatures is the signature of orbital ordering in the presently studied nearly half-doped manganite system. Results of the detailed structural analysis of the temperature-dependent ND measurements on (LaTb) 0.45 (CaSr) 0.55 MnO 3 sample has been discussed in the light of coexisting A-type and CE-type antiferromagnetic phases present in the sample at low temperature.
Applied Surface Science, 2012
Nanostructured polycrystalline La 0.7 Ca 0.3 MnO 3 (LCMO) and Nd 0.7 Sr 0.3 MnO 3 (NSMO) manganit... more Nanostructured polycrystalline La 0.7 Ca 0.3 MnO 3 (LCMO) and Nd 0.7 Sr 0.3 MnO 3 (NSMO) manganites have been successfully synthesized at various temperatures ranging between 700 and 1100 • C using Sol-Gel method. Crystalline nature and morphology of the samples have been studied using XRD (Rietveld analysis) and TEM measurements. SEM studies reveal nanostructured grain morphology of LCMO and NSMO samples. It is observed that, with increase in sintering temperature, crystallinity and grain morphology get improved resulting in better transport. A strong dependence of transport on size variance has been observed in the systems studied. The modified transport and better magnetotransport properties of the manganites have been observed due to the large surface to volume ratio (surface contribution) in the nanostructured manganites. The observation of large low temperature MR in both the manganite systems and the interplay between the intrinsic and extrinsic MR components has been explained in the light of spin polarized tunneling effect, grain morphology, grain boundary nature and size disorder effect.