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Flux dynamics and low-field magnetic properties of the heavy-fermion superconductor CeCu2Si2

Flux dynamics and low-field magnetic properties of the heavy-fermion superconductor CeCu2Si2 Strong flux creep effects are observed in CeCu2Si2 at low magnetic inductions and temperatures in the range 6 mK<T<T c . Measurements of flux creep in single crystal as well as polycrystalline specimens show that the magnetization in CeCu 2 Si 2 decays following a power law time dependence of the typeM(t)∝t −α for 1<t<10 5 sec, where the exponent a ranges between 0.015 and 0.06. The activation energy values obtained from the relaxation rates are around 2–3 meV. The flux creep data give clear evidence of the existence of different types of pinning centers in CeCu 2 Si 2 : a large number of shallow potential barriers that characterize the vortex dynamics at short times and few strong pinning centers responsible for the long-time relaxation behavior. Quantum tunneling of flux lines through weak pinning centers probably gives rise to the non-thermally activated relaxation observed at the lowest temperatures. The physical origin of weak and strong pinning centers in CeCu 2 Si 2 is discussed. From isothermal dc magnetization measurements we estimate the lower critical fieldH c1 as well as the critical current densityJ c . TheH c1 versusT curve shows an anomalous positive curvature for temperatures close toT c . http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Low Temperature Physics Springer Journals

Flux dynamics and low-field magnetic properties of the heavy-fermion superconductor CeCu2Si2

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References (55)

Publisher
Springer Journals
Copyright
Copyright
Subject
Physics; Condensed Matter Physics; Characterization and Evaluation of Materials; Magnetism, Magnetic Materials
ISSN
0022-2291
eISSN
1573-7357
DOI
10.1007/BF00682009
Publisher site
See Article on Publisher Site

Abstract

Strong flux creep effects are observed in CeCu2Si2 at low magnetic inductions and temperatures in the range 6 mK<T<T c . Measurements of flux creep in single crystal as well as polycrystalline specimens show that the magnetization in CeCu 2 Si 2 decays following a power law time dependence of the typeM(t)∝t −α for 1<t<10 5 sec, where the exponent a ranges between 0.015 and 0.06. The activation energy values obtained from the relaxation rates are around 2–3 meV. The flux creep data give clear evidence of the existence of different types of pinning centers in CeCu 2 Si 2 : a large number of shallow potential barriers that characterize the vortex dynamics at short times and few strong pinning centers responsible for the long-time relaxation behavior. Quantum tunneling of flux lines through weak pinning centers probably gives rise to the non-thermally activated relaxation observed at the lowest temperatures. The physical origin of weak and strong pinning centers in CeCu 2 Si 2 is discussed. From isothermal dc magnetization measurements we estimate the lower critical fieldH c1 as well as the critical current densityJ c . TheH c1 versusT curve shows an anomalous positive curvature for temperatures close toT c .

Journal

Journal of Low Temperature PhysicsSpringer Journals

Published: Nov 6, 2004

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