D. Banerjee

Bio: D. Banerjee is an academic researcher from University of Calcutta. The author has contributed to research in topics: Irradiation & Magnetoresistance. The author has an hindex of 5, co-authored 7 publications receiving 57 citations.

In situ monitoring of electrical resistance of nanoferrite thin film irradiated by 190 MeV Au14+ ions

Abstract: A highly resistive nanocrystalline thin film of Li0.25Mg0.5Mn0.1Fe2.15O4, deposited by RF magnetron sputtering technique on Si(1 0 0) substrate, is irradiated with 190 MeV Au14+ ions. To probe the swift heavy ion induced modifications in the electrical properties in the film an in situ measurement of electrical resistance using two-probe method is carried out. We observe the value of resistivity comes down drastically from 1.5 × 108 to 1 × 105 Ω cm after irradiation at the fluence of 1 × 1013 ions/cm2. In XRD spectra after irradiation no previous spinel peaks are observed. No loss in oxygen content with fluence is observed. We have presented the observed phenomenon as an effect of formation of amorphized latent tracks on the basis of thermal spike model.

Effect of Li3+ irradiation on the transport properties of La0.7Pb0.3MnO3 type CMR material

Abstract: We report the low temperature (below the metal–insulator transition temperature Tim) resistivity and magnetoresistance (MR) behavior of 50 MeV Li3+ beam irradiated La0.7Pb0.3MnO3 for three different fluences. Ion beam irradiation causes a decrease of Tim leading to the increase of insulating regime. Resistivity data of the unirradiated as well as irradiated samples fitted well with an equation of the form ρ = ρ0 + ρ2.5T2.5 which indicates predominant contribution from the electron–magnon interaction (second term). The temperature dependent MR data of samples irradiated with different ion fluences follow the simple relation [MR = a + b/(T + C)] showing appreciable effect of radiation on the parameters a, b and C. The physical significance of the radiation effect on these parameters is not yet very clear.

Positron annihilation studies on the La1−xPbxMnO3 system

Abstract: Positron annihilation lifetime studies have been carried out on the La1−xPbxMnO3-type magnetoresistive compounds for x=0.05, 0.1, 0.3, 0.5 and 0.7. Both room-temperature resistivity and mean positron lifetime ( τ ) data show a dip around x=0.3. The magnetic susceptibility of these samples also shows a peak around the same concentration (x=0.3) of Pb. The minimum value of τ around x=0.3 suggests localization of the electrons arising due to strong electron–phonon interaction.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Abstract: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

Annealing effect on nano-ZnO powder studied from positron lifetime and optical absorption spectroscopy

Abstract: Mechanical milling and subsequent annealing in air at temperatures between 210 and 1200°C have been carried out on high purity ZnO powder to study the defect generation and recovery in the material. Lowering of average grain size (from 76±1to22±0.5nm) as a result of milling has been estimated from the broadening of x-ray lines. Substantial grain growth in the milled sample occurs above 425°C annealing temperature. Positron annihilation lifetime (PAL) analysis of the samples shows a distinct decrease of the average lifetime of positrons very near the same temperature zone. As indicated from both x-ray diffraction (XRD) and PAL results, high temperature (>700°C) annealed samples have a better crystallinity (or lower defect concentration) than even the nonmilled ZnO. In contrast, the measured optical band gap of the samples (from absorption spectroscopy) does not confirm lowering of defects with high temperature annealing. Thermally generated defects at oxygen sites cause significant modification of the optical absorption; however, they are not efficient traps for positrons. Different thermal stages of generation and recovery of cationic as well as anionic defects in granular ZnO are discussed in the light of XRD, PAL, and optical absorption studies.

Ion irradiation effects in nanocrystalline TiN coatings

Abstract: Nitride materials and coatings have attracted extensive research interests for various applications in advanced nuclear reactors due to their unique combination of physical properties, including high temperature stability, excellent corrosion resistance, superior mechanical property and good thermal conductivity. In this paper, the ion irradiation effects in nanocrystalline TiN coatings as a function of grain size are reported. TiN thin films (thickness of 100 nm) with various grain sizes (8-100 nm) were prepared on Si substrates by a pulsed laser deposition technique. All the samples were irradiated with He ions to high fluences at room temperature. Transmission electron microscopy (TEM) and high resolution TEM on the ion-irradiated samples show that damage accumulation in the TiN films reduces as the grain size reduces. Electrical resistivity of the ion-irradiated films increases slightly compared with the as-deposited ones. These observations demonstrate a good radiation-tolerance property of nanocrystalline TiN films.