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Neutron Depolarisation by YBa2Cu5O6.85, Superconductors

Published online by Cambridge University Press:  26 February 2011

J. Wang ,
S. J. Kennedy  and
K. N. R.
J. Wang
Affiliation:
School of Materials Science and Engineering, University of New South Wales POB 1, Kensington, NSW 2033, Australia
S. J. Kennedy
Affiliation:
Australian Institute of Nuclear Science and Engineering, PMB 1, Menai, NSW 2234, Australia
K. N. R.
Affiliation:
AEM, School of Physics, University of New South Wales POB 1, Kensington, NSW 2033, Australia
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Abstract

We report a study of magnetic flux penetration into a single crystal superconductor, using the technique of 1-dimensional neutron depolarisation. In these experiments we have applied magnetic fields of up to 1.7 kOe to the crystal, perpendicular to the polarisation direction of the neutron beam. By analysing the polarisation of the transmitted neutron beam, after removal of the applied field, we are able to determine the remanent magnetisation in the crystal as well as its decay over periods from 10 to 105 seconds. This technique allows us to study both field and time dependent behaviour.

We are developing a model to explain these observations, using the Bean critical state model to calculate the bulk trapped flux with the assumption of simple spin precession in a uniaxial magnetic environment. We have been able to relate the field dependence of the remanent magnetisation to the lower critical field Hcl and the field at which magnetisation saturation is reached 2H*-Hcl. We also relate the time dependence to the flux pinning energy U which determines the rate of flux relaxation. Measurements of this type could be used to plot the magnetic phase diagram of high temperature superconductors, to study anisotropy and flux creep in such crystals.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 275: Symposium S – Layered Superconductors: Fabrication, Properties and Applications , 1992 , 193
Copyright
Copyright © Materials Research Society 1992

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References

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