M.S. Sahasrabudhe

Bio: M.S. Sahasrabudhe is an academic researcher from Savitribai Phule Pune University. The author has contributed to research in topics: Thin film & Magnetoresistance. The author has an hindex of 4, co-authored 6 publications receiving 47 citations.

Swift ion irradiation induced changes in the structural and transport properties of La0.7Sr0.3MnO3 thin films

Abstract: Highly c -axis oriented, magnetoresistive thin films of La 0.7 Sr 0.3 MnO 3 deposited on LaAlO 3 (1 0 0) (LAO) substrates by pulsed laser deposition have been subjected to thermal annealing and subsequently to irradiation with swift heavy ions. While the as-deposited films show insulator metal transition T p at ∼265 K, the annealed films show metallic behavior over a wide temperature range viz. from 125 K to 400 K. We have investigated the effect of 90 MeV O 7+ ions and 200 MeV Ag 15+ ions on structural and electrical properties of these films. Dose values ranging from 1 × 10 12 to 1 × 10 14 ions/cm 2 of O 7+ ions and from 1 × 10 11 to 1 × 10 12 ions/cm 2 of Ag 15+ ions were used. The metal–insulator transition reoccurs in the irradiated films and the T p can be tailored to room temperature with irradiation dose value and energy of the ion. Attempt is made to comprehend this variation in T p on the basis of swift ion irradiation induced defects and related strain rather than change in oxygen content of the films.

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

Abstract: The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La1−2x Pr x Ca x )MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.

Effect of swift heavy ion irradiation on the surface morphology of highly c-axis oriented LSMO thin films grown by pulsed laser deposition

Abstract: A detailed investigation of the surface morphology of the pristine and swift heavy ion (SHI) irradiated La 0.7 Sr 0.3 MnO 3 (LSMO) thin film using atomic force microscope (AFM) is presented. Highly c -axis oriented LSMO thin films were grown on LaAlO 3 (1 0 0) (LAO) substrates by the pulsed laser deposition (PLD) technique. The films were annealed at 800 °C for 12 h in air (pristine films) and subsequently, irradiated with SHI of oxygen and silver. The incident fluence was varied from 1 × 10 12 to 1 × 10 14 ions/cm 2 and 1 × 10 11 to 1 × 10 12 ions/cm 2 for oxygen and silver ions, respectively. X-ray diffraction (XRD) studies reveal that the irradiated films are strained. From the AFM images, various details pertaining to the surface morphology such as rms roughness ( σ ), the surface rms roughness averaged over an infinite large image ( σ ∞ ), fractal dimension ( D F ) and the lateral coherence length ( ξ ) were estimated using the length dependent variance measurements. In case of irradiated films, the surface morphology shows drastic modifications, which is dependent on the nature of ions and the incident fluence. However, the surface is found to remain self-affine in each case. In case of oxygen ion irradiated films both, σ ∞ and D F are observed to increase with fluence up to a dose value of 1 × 10 13 ions/cm 2 . With further increase in dose value both σ ∞ and D F decreases. In case of silver ion irradiated films, σ ∞ and D F decrease with increase in fluence value in the range studied.

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.

Room temperature positive magnetoresistance and field effect studies of manganite-based heterostructure

Abstract: We report the results of studies of rectifying behavior, positive magneoresistance (MR), the charge-transport mechanism and the effect of an electric field on a ZnO (n)/La0.5Pr0.2Sr0.3MnO3 (LPSMO) (p)/SrNb0.002Ti0.998O3 (SNTO) (n) heterostructure comprising two p–n junctions fabricated using the pulsed laser deposition technique. The heterostructure exhibits rectifying behavior over a wide temperature and field range having hysteresis in I–V behavior (forward bias) due to the tunneling of charge carriers. It is also observed that, depending on the nature of the electric field bias to n-type ZnO and SNTO, the junction resistance becomes modified, which has been explained on the basis of spin injection in the heterostructure. The observation of unconventional positive MR at room temperature has been justified on the basis of interface effects and the reduction in barrier height obtained using fitting of the I–V data by a thermionic emission model.

Electric–dielectric properties and complex impedance analysis of La0.5Ca0.5−xAgxMnO3 manganites

Abstract: The electric and dielectric properties of La0.5Ca0.5−xAgxMnO3 (LCMO–Ag with x = 0 and x = 0.4) were investigated using the impedance spectroscopy technique. For the free compound, conductivity analysis proved the absence of a metal–semiconductor transition in the temperature range of 80 K to 700 K. When silver was introduced, such transition appears at around TMS = 200 K. We found that the conduction mechanism was governed by small polaron hopping (SPH) in the high temperature region and by variable range hopping (VRH) in the low temperature region. Several results were deduced from the complex impedance analysis (CIA). First, a non-Debye relaxation phenomenon in the system was observed. Second, the CIA permitted us to model the compounds in terms of an electrical equivalent circuit. Moreover, this study confirmed the contribution of the grain boundary in the transport properties. It was found that the activation energy deduced from the conductivity, the relaxation time and the grain boundary were close to each other. The dielectric constant and dielectric loss were investigated. For the free compound, the dielectric transition was not observed in the investigated temperature range but, for the doped compound, the dielectric transition appeared at Td = 200 K. The Td value was close to the TMS value. The thermal evolution of the real part of dielectric permittivity is described by the Curie–Weiss law. From the variation of the imaginary part of the dielectric permittivity and the dielectric loss versus temperature at different frequencies, we found that the free compound had a typical behavior of a relaxor but the doped one had a typical behavior of a normal dielectric.