Normal-state properties of high-angle grain boundaries in $(\mathrm{Y},\mathrm{Ca}){\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$

Normal-state properties of high-angle grain boundaries in $(Y, Ca) {Ba}_{2} {Cu}_{3} O_{7 - δ}$

S. H. Mennema, J. H. T. Ransley, G. Burnell, J. L. MacManus-Driscoll, E. J. Tarte, and M. G. Blamire

Phys. Rev. B 71, 094509 – Published 18 March 2005

Abstract

By lithographically fabricating an optimized Wheatstone bridge geometry, we have been able to make accurate measurements of the resistance of grain boundaries in $Y_{1 - x} {Ca}_{x} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ between the superconducting transition temperature $T_{c}$ and room temperature. Below $T_{c}$ , the normal-state properties were assessed by applying sufficiently high currents. The behavior of the grain boundary resistance versus temperature and of the conductance versus voltage are discussed in the framework charge transport through a tunnel barrier. The influence of misorientation angle, oxygen content, and calcium doping on the normal-state properties is related to changes of the height and shape of the grain boundary potential barrier.

Received 27 August 2004

DOI:https://doi.org/10.1103/PhysRevB.71.094509

Authors & Affiliations

S. H. Mennema, J. H. T. Ransley, G. Burnell, J. L. MacManus-Driscoll, E. J. Tarte, and M. G. Blamire

Department for Materials Science and Metallurgy, University of Cambridge, Pembroke Street, CB2 3QZ, Cambridge, United Kingdom

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Vol. 71, Iss. 9 — 1 March 2005

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Figure 1
(a) Resistance × area values for grain boundaries in $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ . The misorientation angles of the grain boundaries range, as indicated, from 18° to 45°. The inset shows the resistance × area values for the four highest misorientation angles normalized at $300 K$ . (b) Resistance × area values for grain boundaries with misorientation angles between 24° and 45° in $Y_{0.8} {Ca}_{0.2} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ . The inset shows the resistance × area values normalized at $300 K$ .Reuse & Permissions
Figure 2
(a) Resistance × area values for 30° grain boundaries in $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ and in $Y_{0.8} {Ca}_{0.2} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ . Results for samples with reduced oxygen content are also shown. The arrows indicate the change of the resistance vs temperature characteristic due to a decreased oxygen content. The behavior of a grain boundary with a misorientation angle of 37° in $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ is shown for comparison. (b) All resistance vs temperature characteristics of Fig. 2a normalized at $300 K$ . The arrows indicate the change of the temperature dependence of the resistance due to a decreased oxygen content.Reuse & Permissions
Figure 3
(a) Current-voltage characteristics at $6 K$ of grain boundaries in $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ with misorientation angles between 24° and 45°. (b) Current-voltage characteristics of grain boundaries in $Y_{0.8} {Ca}_{0.2} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ . Note that the x- and y-axis scales are identical in (a) and (b).Reuse & Permissions
Figure 4
Differential conductivity $(G = δ J ∕ δ V)$ at $6 K$ as a function of voltage for grain boundaries with three different misorientation angles in $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ and $Y_{0.8} {Ca}_{0.2} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ films. These $G (V)$ characteristics were extracted from the $J (V)$ characteristics in Fig. 3. Note that the scale at the y axis is logarithmic. Some data points close to zero voltage are removed because of the Josephson current peak. The proposed difference in shape of the potential barrier is qualitatively represented for grain boundaries with misorientation angles of 30° and 37°/45°.Reuse & Permissions
Figure 5
Differential conductivity $(G = δ J ∕ δ V)$ as a function of voltage for grain boundaries with a misorientation angle of 45° in (a) $Y {Ba}_{2} {Cu}_{3} O_{7 - δ}$ and (b) $Y_{0.8} {Ca}_{0.2} {Ba}_{2} {Cu}_{3} O_{7 - δ}$ films. Conductivity data are shown for a range of temperatures with intervals of $6 K$ between (a) $6$ and $84 K$ and (b) 6 and $66 K$ . Note that the (linear) x- and y-axis scales are not identical in (a) and (b). Noise features have been removed from these data using a fast Fourier transform smoothing routine.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Normal-state properties of high-angle grain boundaries in $(Y, Ca) {Ba}_{2} {Cu}_{3} O_{7 - δ}$

S. H. Mennema, J. H. T. Ransley, G. Burnell, J. L. MacManus-Driscoll, E. J. Tarte, and M. G. Blamire

Phys. Rev. B 71, 094509 – Published 18 March 2005

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Physical Review B

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Normal-state properties of high-angle grain boundaries in (Y,Ca)Ba2Cu3O7−δ

S. H. Mennema, J. H. T. Ransley, G. Burnell, J. L. MacManus-Driscoll, E. J. Tarte, and M. G. Blamire

Phys. Rev. B 71, 094509 – Published 18 March 2005

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Normal-state properties of high-angle grain boundaries in $(Y, Ca) {Ba}_{2} {Cu}_{3} O_{7 - δ}$