Eur. Phys. J. B 47, 231-237 (2005)
https://doi.org/10.1140/epjb/e2005-00322-1

Doping dependence of the vortex glass and sublimation transitions in the high-T_c superconductor La_2-xSr_xCuO₄ as determined from macroscopic measurements

¹ Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, 5232 Villigen PSI, Switzerland
² Departement of Physics, Hokkaido University, Sapporo 060-0810, Japan

Corresponding author: ^a gilardi@hispeed.ch

Received: 3 April 2005
Revised: 25 July 2005
Published online: 11 October 2005

Abstract

Magnetization and ac-susceptibility measurements are used to characterize the mixed phase of the high-temperature cuprate superconductor La_2-xSr_xCuO₄ over a large range of doping (0.075  0.20). The first order vortex lattice phase transition line , the upper critical field and the second peak have been investigated up to high magnetic fields (8 Tesla applied perpendicular to the planes). Our results reveal a strong doping dependence of the magnetic phase diagram, which can mainly be explained by the increasing anisotropy with underdoping. Within our interpretation, the first order vortex lattice phase transition is due to the sublimation (rather than melting) of the vortex lattice into a gas of pancake vortices, whereas the second peak is related to the transition to a more disordered vortex glass state.