Point-contact measurements of CeB6 and CeCu6 in high magnetic fields |
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Authors: | Yu G Naidyuk M Reiffers A G M Jansen P Wyder I K Yanson |
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Institution: | (1) Institut für Festkörperphysik, Technische Hochschule, Hochschulstrasse 8, W-6100 Darmstadt, Federal Republic of Germany |
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Abstract: | Epitaxial YBa2Cu4O7-thin films with thec-axis oriented perpendicular to the film plane were prepared bydc-sputtering from a single stoichiometric target on (100) SrTiO3-substrates. Typical values of the inductively measured superconducting transitions were about 90 K with a width less than 0.5 K. Critical current densities were measured on 5 to 10 m wide strips as function of magnetic field and temperature. The temperature dependences ofj
c
follow a universal functionj
c(B,T)=j
c
*
(T=0,B)·(1–T/T
c
(B)) with =1.5±0.1. ForB=0 andT=77 K we obtainedj
c
=4·106 A/cm2. The field dependence of the resistive transitions was measured with the magnetic field parallel to thec-axis. The slope of the upper critical fieldB
c2 (T) was determined for different criteria. The carrier concentration evaluated from Hall-effect measurements was found to decrease linearly from one per unit cell at 240 K with decreasing temperature extrapolating nearly through zero forT=0. Highly resolved angular dependent measurements of the critical current density withB perpendicular to the current but tilted from thec-axis show a very strong and sharp enhancement ofj
c
for the magnetic field parallel to the (CuO2)-layers (B c). Additionally to this phenomenon, which is caused by an intrinsic pinning mechanism due to the layered structure of high-T
c
-superconductors the influence of the anisotropy of the upper critical field onj
c
(B, T, ) is evident nearT
c
. |
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Keywords: | |
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