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29 Jan 2001

Volume 78, Issue 5, pp. 563-679

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Tuning colossal magnetoresistance response by Cr substitution in La0.67Sr0.33MnO3

Young Sun, Wei Tong, Xiaojun Xu, and Yuheng Zhang

Appl. Phys. Lett. 78, 643 (2001); http://dx.doi.org/10.1063/1.1344229 (3 pages) | Cited 22 times

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We have studied the effects of Cr substitution in the perovskite La0.67Sr0.33MnO3 on the magnetic, electrical transport, and magnetoresistance properties. Cluster glass behaviors have been observed in the La0.67Sr0.33Mn1−xCrxO3 system. The most interesting feature is that extraordinary transport and colossal magnetoresistance (CMR) behaviors, characterized by double peaks, were observed with Cr substitution. When 0.1 ⩽ x ⩽ 0.2, the temperature range of CMR response is greatly broadened, from the lowest temperature to above room temperature. These results suggest that Cr substitution can be a potent way in tuning CMR response and also imply a ferromagnetic interaction similar to double exchange occurs between Mn and Cr. © 2001 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Microwave surface resistance of YBa2Cu3Oy films covered by overdoped Y1−xCaxBa2Cu3Oy layers

H. Obara, A. Sawa, H. Yamasaki, and S. Kosaka

Appl. Phys. Lett. 78, 646 (2001); http://dx.doi.org/10.1063/1.1343473 (3 pages) | Cited 9 times

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We have observed the reduction of the microwave surface resistance Rs of YBa2Cu3Oy films deposited on MgO substrates by covering the films with an overdoped Y1−xCaxBa2Cu3Oy layer. At low temperature, Rs of the YBa2Cu3Oy film covered by an Y1−xCaxBa2Cu3Oy (x = 0.2) layer was half that of the single YBa2Cu3Oy film. On the other hand, the single Y1−xCaxBa2Cu3Oy (x = 0.2) films did not exhibit low loss characteristics. The diffusion of Ca ions into the YBa2Cu3Oy layer was observed and the selective diffusion of Ca ions to the grain boundaries of the YBa2Cu3Oy layer is considered to be the origin of the low Rs in the covered YBa2Cu3Oy films. © 2001 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
72.30.+q High-frequency effects; plasma effects
73.25.+i Surface conductivity and carrier phenomena
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.72.Mm Grain and twin boundaries
74.25.F- Transport properties
74.25.N- Response to electromagnetic fields

Accurate comparative measurement of oxygen content variations in YBa2Cu3O7−δ films due to postdeposition annealing

H. Y. Zhai, Z. H. Zhang, and W. K. Chu

Appl. Phys. Lett. 78, 649 (2001); http://dx.doi.org/10.1063/1.1344571 (3 pages) | Cited 1 time

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Non-Rutherford elastic resonance scattering, 16O(α,α)16O at 3.045 MeV, has been used to measure the change in relative oxygen content, δ of dc-sputtered YBa2Cu3O7−δ (YBCO) films due to postdeposition annealing to a precision of 1%. Experimental results show that only 3.4% of the total amount of oxygen in YBa2Cu3O7−δ is absorbed in the postdeposition annealing process, and this agrees with our x-ray diffraction data. The presence of oxygen during annealing, which leads to the transition to the superconducting orthorhombic structure, may also be understood as providing a more favorable environment for structure reformation, rather than only adding more oxygen into the YBCO film. © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
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