Papers by Sudipta Bandyopadhyay
Effect of Co Doping on Structural and Magnetic Properties of Kagome Like La Based Cuprate Francisite Cu3la(Seo3)2o2cl
SSRN Electronic Journal
Influence of Ion Beam Irradiation on Optical and Magnetic Properties of Transparent Mn Doped ZnO Thin Films, Suitable for Sensor Applications
ECS Journal of Solid State Science and Technology
The present work describes modification in physical properties of Zn0.95Mn0.05O films by ion beam... more The present work describes modification in physical properties of Zn0.95Mn0.05O films by ion beam irradiation. Films were prepared by spin coating and annealed at 500 °C. XRD patterns of these films show wurzite structure with good crystalline quality. However, Low energy irradiation could modify and induces new defect states. Characterization of those defects had been performed by analysing the UV-Visible absorption spectroscopy and Photoluminescence (PL) spectroscopy. Room temperature PL emission of Zn0.95Mn0.05O film shows a broad UV emission and pronounced visible emission ∼530 nm. At low temperature broad UV band become more prominent however it is completely quenched after irradiation. For all irradiated films we had notice only visible emission of comparable intensities, confined within the region 475 nm to 550 nm. Irradiated films are showing ferromagnetism at room temperature and most importantly the film irradiated at fluence F: 1016 ions cm−2 exhibit maximum saturation ma...
低エネルギーイオン照射および非照射Zn_0Cu3O6.95Mn_0 0.05O膜の磁気的性質と微細構造特性との相関【Powered by NICT】
We have investigated the structural and physical properties of double perovskite (DP) LaAVMoO6 (A... more We have investigated the structural and physical properties of double perovskite (DP) LaAVMoO6 (A= Ca,Sr ,Ba ; abbreviated as LCVMO, LSVMO, and LBVMO from now onwards) compounds as possible half metallic antiferromagnet (HM-AFM) candidates. The more prominent member of this series is LaSrVMoO6 (LSVMO) which was actually claimed to be a HM-AFM in presence of substantial V/Mo ordering 1,2 . However, we have earlier shown that other than the complex issue of A-(La/Sr) and B-(V/Mo) site ordering within the given DP structure, strong La-O covalency brings forth another important parameter which dominates the site-disorder issues and introduces an unusual microscopic phase separation in LSVMO 3,4 . It is evident that substitution of Sr 2+ by Ca 2+ and Ba 2+ at the A-site would offer a tool to modify the A-site ordering and thereby manipulating the above mentioned phase separation, which is entirely driven by La-O covalency. Our experimental results reveal 5 that LCVMO sits at the extreme ...
Journal of Alloys and Compounds, 2021
Nanocomposites (NCs) containing strontium hexaferrite (SrFe 12 O 19 , SFO) and dysprosium-substit... more Nanocomposites (NCs) containing strontium hexaferrite (SrFe 12 O 19 , SFO) and dysprosium-substituted bismuth ferrite (Bi 0.9 Dy 0.1 FeO 3 , BDFO) with composition x SrFe 12 O 19-(1-x) Bi 0.9 Dy 0.1 FeO 3 , with x ¼ 0.1, 0.2, and 0.3, have been synthesized using the sol-gel route and their structural, magnetic, dielectric and magnetoelectric properties have been investigated. Formation of pure crystalline x SFO-(1-x) BDFO NCs is confirmed by XRD measurements. Magnetization and dielectric constant (ε r) of the pristine BiFeO 3 (BFO) have been found to increase on Dy-substitution. In the nanocomposite samples, magnetization increases, but dielectric constant decreases with increasing SFO content. Variation of capacitance of the NC samples in the presence of magnetic field up to 150 kOe indicates a substantial enhancement of the magnetoelectric (ME) coupling coefficient of BFO in the nanocomposites. ME coupling tends to improve with higher SFO content in the NCs.
Applied Surface Science, 2019
3 at% Co doped sol-gel derived films were irradiated with 800 keV Ar ion beam. The studied films ... more 3 at% Co doped sol-gel derived films were irradiated with 800 keV Ar ion beam. The studied films were un-irradiated and irradiated with fluences 5 x 10 14 , 2.5 x 10 15 and 10 16 ions/cm 2. The films were characterized structurally (X-ray diffraction [XRD]), morphologically (Field Induced Scanning Electron Microscopy), optically (UV-visible, Raman spectroscopy and Photoluminescence [PL] measurements), magnetically (field and temperature dependent magnetization measurements) and electronically via local structure study (X-ray Absorption spectroscopy [XAS]). XAS data were interpreted in X-ray absorption near edge spectroscopy (XANEX) and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements. XRD patterns show single-phase wurtzite structure of the films and indicate presence of defects. Raman spectra confirm single-phase structure of the films and indicate slight structural degradation in highest fluence irradiated film. The high substitutional incorporation of Co 2+ at Zn 2+ site was demonstrated from UV-visible spectra by d-d transition. The analysis of XANES and EXAFS spectra strongly reconfirms further the proper substitutional incorporation of Co 2+ at Zn 2+ site. All films are intrinsically ferromagnetic. The substantial enhancement of ferromagnetism (2.5 fold) has been observed upon irradiation (highest fluence) and it has been interpreted in terms of defects as evidenced from PL measurement. Hence the effect of Ar ion beam irradiation is highly enhanced ferromagnetism and proper Co substituted ZnO film.
Local Structure Investigation of Mn- and Co-Doped TiO2 Thin Films by X-Ray Absorption Spectroscopy
ChemistrySelect, 2017
IEEE Transactions on Electron Devices, 2017
In this literature, we have investigated the magnetic properties and Schottky device-based charge... more In this literature, we have investigated the magnetic properties and Schottky device-based charge transport properties of hydrothermally derived Mn 0.04 Cu 0.05 Zn 0.91 O nanorod. The doping of 3-D transitional metals, Mn and Cu, within ZnO makes it potentially applicable in spin-based electronics, whereas its temperature-dependent conductivity (of the order of 10 −3 in C.G.S.) makes it suitable for semiconductor-based devices. The observation of intrinsic ferromagnetism of the synthesized composite and its variation of magnetization with magnetic field and temperature exhibited the suitability of spin-based electronic application. To check the applicability in optoelectronic devices, metal-semiconductor (Al/Mn 0.04 Cu 0.05 Zn 0.91 O) junction was fabricated and analyzed. The current-voltage characteristic represented the rectifying behavior of the junction with on/off current ratio 4.3 at ±1 V in dark and potential barrier height 0.61 eV. The significant change in rectification due to the influence of incident radiation makes this material suitable for photosensing electronic device application.
Journal of Alloys and Compounds, 2018
Modified dielectric and magnetic properties of Fe and Co substituted TbMnO 3 nanoparticles
An organic phase transmetallation approach for synthesis of hollow Ni–Au nanocomposites with tunable cavity size
New Journal of Chemistry, 2018
Hydrophobized HAuCl4 entered Ni nanoparticles through the fractures on the surface initiating tra... more Hydrophobized HAuCl4 entered Ni nanoparticles through the fractures on the surface initiating transmetallation at the centre, yielding hollow Ni–Au composites.
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Journal of physics. Condensed matter : an Institute of Physics journal, Jan 23, 2018
Cubic half-Heusler Cu Co MnSb ([Formula: see text]) compounds have been investigated both experim... more Cubic half-Heusler Cu Co MnSb ([Formula: see text]) compounds have been investigated both experimentally and theoretically for their magnetic, transport and electronic properties in search of possible half metallic antiferromagnetism. The systems (Cu,Co)MnSb are of particular interest as the end member alloys CuMnSb and CoMnSb are semi metallic (SM) antiferromagnetic (AFM) and half metallic (HM) ferromagnetic (FM), respectively. Clearly, Co-doping at the Cu-site of CuMnSb introduces changes in the carrier concentration at the Fermi level that may lead to half metallic ground state but there remains a persistent controversy whether the AFM to FM transition occurs simultaneously. Our experimental results reveal that the AFM to FM magnetic transition occurs through a percolation mechanism where Co-substitution gradually suppresses the AFM phase and forces FM polarization around every dopant cobalt. As a result a mixed magnetic phase is realized within this composition range while a nea...
Applied Surface Science, 2017
Composites comprising of metallic nanoparticles in polymer matrices have allured significant impo... more Composites comprising of metallic nanoparticles in polymer matrices have allured significant importance due to multifunctionalities. Here a simple protocol has been described to embed Ni nanoparticles in carboxymethyl guar gum (CMGG) polymer. The composite formation helps in the stabilization of Ni nanoparticles which are otherwise prone towards aerial oxidation. Further the nanoparticles retain their superparamagnetic nature and catalytic capacity. Ni-Polymer composite catalyses the reduction of 4-Nitrophenol to 4-Aminophenol very efficiently in presence of NaBH 4 , attaining a complete conversion under some experimental conditions. Ni-Polymer composite is well characterized using UV-vis spectroscopy, FTIR, XPS, powder XRD, TGA, SEM and TEM. A detailed magnetic measurement using superconducting quantum interference device-vibrating sample magnetometer (SQUID-VSM) reveals superparamagnetic behaviour of the composite.
ChemistrySelect, 2017
TM 0.03 Zn 0.97 O (TM: Mn, Fe, Co and Ni) nanoparticles have been synthesized using sol-gel techn... more TM 0.03 Zn 0.97 O (TM: Mn, Fe, Co and Ni) nanoparticles have been synthesized using sol-gel technique. Structural study through X-ray diffraction (XRD) has revealed that all samples, except Ni:ZnO, possess single phase wurtzite structure of ZnO, whereas in Ni:ZnO, Ni ions have mainly segregated as NiO (a secondary phase). Morphological study through Field Effect Scanning Electron Microscopy (FESEM) has confirmed the formation of nanoparticles with particle sizes in the range of 30-61 nm. X-ray absorption spectroscopy (XAS) exhibits that Co ions substitutionally replace Zn ions, Mn ions partially occupy substitutional sites and partially interstitial positions, Fe ions mainly occupy interstitial positions, whereas Ni ions mainly chemically segregate with oxygen to form NiO phase. All TM:ZnO samples show reasonable ferromagnetism (FM) up to room temperature (RT) and except for the Ni:ZnO, the observed FM seems to be intrinsic in nature. Temperature dependent magnetization (MÀT) measurement of Ni:ZnO reveals a superparamagnetic behavior (with transition temperature higher than 300 K). In the regime of diluted magnetic semiconductors (DMSs) and as far as intrinsic FM is concerned, Fe:ZnO sample seems to be a good ferromagnet with appreciable saturation magnetization (M S),whereas Co:ZnO shows hard FM (with significant irreversible magnetization). The higher capability of occupying substitutional position by Co ions enhances further the utility of Co:ZnO.
Physical Review B, 2017
We have investigated the structural and physical properties of double perovskite (DP) LaAVMoO 6 (... more We have investigated the structural and physical properties of double perovskite (DP) LaAVMoO 6 (A = Ca 2+ , Ba 2+ ; abbreviated as LCVMO and LBVMO from now on) compounds, proposed to be possible half-metallic antiferromagnets (HMAFMs). Here we show that within LaAVMoO 6 double perovskite structure, La-O covalency competes against B-site as well A-site cationic order and this competition critically influences their physical properties. Evidently, the presence of Ca 2+ or Ba 2+ at the A site along with La 3+ would offer a tool to modify the A-site ordering and consequently influence the La-O covalency as well. Our experimental results reveal that LCVMO lies at the extreme end of this family and accommodates large scale phase separation in terms of La, V, and Ca, Mo-rich phases as a result of dominant La-O covalency. On the other hand, LBVMO is more correctly described as a layered A-site ordered and nearly complete B-site disordered double perovskite where cationic order dominates the La-O covalency. The general trend of our experimental findings is in agreement with the ab initio electronic structure calculations, carried out on realistic structures based on local coordination obtained from extended x-ray-absorption fine-structure study.
Journal of Applied Physics, 2016
Nanocomposites (NCs) comprising (1Àx) BiFeO 3 (BFO) and x SrFe 12 O 19 (SRF) (x ¼ 0.1, 0.2, 0.3, ... more Nanocomposites (NCs) comprising (1Àx) BiFeO 3 (BFO) and x SrFe 12 O 19 (SRF) (x ¼ 0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO 3 (BFO) and SrFe 12 O 19 (SRF) in the NCs for x ¼ 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x ¼ 0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10 K indicate predominantly ferrimagnetic behavior of all the NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (e r) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. e r À T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates magnetoelectric coupling in the NCs. The variation of capacitance in the presence of magnetic field confirms the enhancement of magnetoelectric effect in the NCs. 57 Fe M€ ossbauer spectroscopy results indicate the presence of only Fe 3þ ions in usual crystallographic sites of BFO and SRF.
Structural and thermoelectric property study of Se doped Sb2Te3 alloy
In depth structural analysis of the polycrystalline Sb2Te3-xSex alloy has been done by Rietveld r... more In depth structural analysis of the polycrystalline Sb2Te3-xSex alloy has been done by Rietveld refinement technique using MAUD software. Thermal variation of resistivity measurement is performed down to 10 K. Temperature dependent thermopower, measured in the range 300-20 K, reveals that samples are p-type in nature. Power factor has been estimated using resistivity and thermopower data.
New Journal of Chemistry, 2015
A facile method for the synthesis of NicoreAgshell and NicoreAushell nanoparticles with suitable ... more A facile method for the synthesis of NicoreAgshell and NicoreAushell nanoparticles with suitable surface modification for the latter has been demonstrated with potential applications.
Ion Beam–Induced Modification of ZnO-Based Dilute Magnetic Semiconductor
Radiation Synthesis of Materials and Compounds, 2013
Role Of Nano Size Particle Assembly In Ferromagnetism Of Mn Doped ZnO Pellets
ABSTRACT 4 at% Mn doped ZnO samples were synthesized by solid-state reaction technique. Structura... more ABSTRACT 4 at% Mn doped ZnO samples were synthesized by solid-state reaction technique. Structural and magnetic properties were explored. The sample contains a secondary phase of ZnMn2O4 that has transition temperature around 40 K. It shows room temperature (RT) ferromagnetism. The ferromagnetic (FM) part of magnetization is successfully decoupled from PM counterpart by mathematical modeling. The field and temperature dependent magnetization measurements confirm the intrinsic FM nature of the sample. Particle size distribution in nanometer length scale is responsible for typical behavior of temperature dependent magnetization curve.
Absence of Ferromagnetism in Mn Doped ZnO
AIP Conference Proceedings, 2011
2 and 4 at% Mn doped ZnO samples were synthesized by sol‐gel technique. The structural, compositi... more 2 and 4 at% Mn doped ZnO samples were synthesized by sol‐gel technique. The structural, compositional and magnetic properties were investigated. The 4 at% Mn doped sample contains secondary phase of ZnMnO3. The compositions of the samples are close to perfection. Crystallite size decreases with increase in doping. Both samples indicate absence of ferromagnetism. Strong presence of antiferromagnetism was found and it falls with increasing Mn doping. Simultaneously paramagnetic fraction of spin increases.
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Papers by Sudipta Bandyopadhyay