Inhomogeneity of the intrinsic magnetic field in superconducting YBa 2Cu3OX compounds as revealed by a rare-earth EPR probe

Abstract

X-band electron paramagnetic resonance experiments on doped Er 3+ and Yb3+ ions in YBa2Cu3O X (6<X<7) compounds with different oxygen contents in a wide temperature range (4-120 K) have been performed. In the superconducting species at temperatures significantly below TC, strong dependences of the linewidth and resonance line position on the sweep direction of the applied magnetic field are revealed. The possible origins of the observed hysteresis are analysed. The applicability of the presented EPR approach to extract information about the dynamics of the flux-line lattice and critical state parameters (critical current density, JC, magnetic penetration depth, λ, and characteristic spatial scale of the inhomogeneity) is discussed. © 2005 IOP Publishing Ltd.