Relaxation of the magnetization in high-T c superconductors

Abstract

Logarithmic time decays of the magnetization M have been observed in Sr La Cu O and Ba La Cu O specimens. If a small field H i < H C1 is applied to a virgin specimen, the isothermal dc magnetization M is unstable and decays in time following the law M−M 0 αTH i n1n(t/t 0) with n ⋍ 3 over an observation period of 10 5 sec. If the field H i is removed, the same law is followed at H = 0 with a logarithmic rate ∂M/∂lnt about a factor of three smaller. This indicates that these substances have a strong “memory” of the field H i applied previously.