Magnetic-fieldinduced 3D-to-1D crossover in

Received: 5 June 2007
Accepted: 11 July 2007

Abstract

The effect of the magnetic field on the critical behavior of Sr_0.9La_0.1CuO₂ is explored in terms of reversible magnetization data. As the correlation length transverse to the magnetic field H_i, applied along the i-axis, cannot grow beyond the limiting magnetic length , related to the average distance between vortex lines, one expects a magnetic-fieldinduced finite-size effect. Invoking the scaling theory of critical phenomena we provide clear evidence for this effect. It implies that in type-II superconductors there is a 3D-to-1D crossover line with and denotes the critical amplitude of the correlation length below T_c. Consequently, below T_c and above superconductivity is confined to cylinders with diameter (1D). Accordingly, there is no continuous phase transition in the -plane along the -lines as predicted by the mean-field treatment.