115 research outputs found

    A facility for conducting field investigations with radioactive materials

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    Magnesium deficiency on Columbiana County soils

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    Reducing the Uptake of Sr90 by Plants on Contaminated Ohio Soils

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    Author Institution: Department of Agronomy, Ohio Agricultural Experiment Station, Wooster, Ohi

    Effect of Strain Relaxation on Magnetotransport properties of epitaxial La_0.7Ca_0.3MnO_3 films

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    In this paper, we have studied the effect of strain relaxation on magneto-transport properties of La_0.7Ca_0.3MnO_3 epitaxial films (200 nm thick), which were deposited by pulsed laser deposition technique under identical conditions. All the films are epitaxial and have cubic unit cell. The amount of strain relaxation has been varied by taking three different single crystal substrates of SrTiO_3, LaAlO_3 and MgO. It has been found that for thicker films the strain gets relaxed and produces variable amount of disorder depending on the strength of strain relaxation. The magnitude of lattice relaxation has been found to be 0.384, 3.057 and 6.411 percent for film deposited on SrTiO_3, LaAlO_3 and MgO respectively. The films on LaAlO_3 and SrTiO_3 show higher T_{IM} of 243 K and 217 K respectively as compared to T_{IM} of 191 K for the film on MgO. Similarly T_C of the films on SrTiO_3 and LaAlO_3 is sharper and has value of 245 K and 220 K respectively whereas the TC of the film on MgO is 175 K. Higher degree of relaxation creates more defects and hence TIM (T_C) of the film on MgO is significantly lower than of SrTiO_3 and LaAlO_3. We have adopted a different approach to correlate the effect of strain relaxation on magneto-transport properties of LCMO films by evaluating the resistivity variation through Mott's VRH model. The variable presence of disorder in these thick films due to lattice relaxation which have been analyzed through Mott's VRH model provides a strong additional evidence that the strength of lattice relaxation produces disorder dominantly by increase in density of defects such as stacking faults, dislocations, etc. which affect the magneto-transport properties of thick epitaxial La_0.7Ca_0.3MnO_3 films

    High magnetic field transport measurement of charge-ordered Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 strained thin films

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    We have investigated the magnetic-field-induced phase transition of charge-ordered (CO) Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 thin films, deposited onto (100)-oriented LaAlO3_3 and (100)-oriented SrTiO3_3 substrates using the pulsed laser deposition technique, by measuring the transport properties with magnetic fields up to 22T. The transition to a metallic state is observed on both substrates by application of a critical magnetic field (HC>10TH_C>10T at 60K). The value of the field required to destroy the charge-ordered insulating state, lower than the bulk compound, depends on both the substrate and the thickness of the film. The difference of the critical magnetic field between the films and the bulk material is explained by the difference of in-plane parameters at low temperature (below the CO transition). Finally, these results confirm that the robustness of the CO state, depends mainly on the stress induced by the difference in the thermal dilatations between the film and the substrate.Comment: 10 pages, 6 figures. To be published in Phys. Rev.

    Electronic phase transitions in Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 epitaxial thin films revealed by resonant soft x-ray scattering

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    We report the study of magnetic and orbital order in Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 epitaxial thin films grown on (LaAlO3_3)0.3_{0.3}-(SrAl0.5_{0.5}Ta0.5_{0.5}O3_3)0.7_{0.7} (LSAT) (011)c_c. In a new experimental approach, the polarization and energy dependence of resonant soft x-ray scattering are used to reveal significant modifications of the magnetic order in the film as compared to the bulk, namely (i) a different magnetic ordering wave vector, (ii) a different magnetic easy axis and (iii) an additional magnetic reordering transition at low temperatures. These observations indicate a strong impact of the epitaxial strain on the spin order, which is mediated by the orbital degrees of freedom and which provides a promising route to tune the magnetic properties of manganite films. Our results further demonstrate that resonant soft x-ray scattering is a very suitable technique to study the magnetism in thin films, to which neutron scattering cannot easily be applied due to the small sample volume.Comment: 5 pages, 3 figure
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