Phase separation kinetics in La2CuO4 + δ and inhomogeneous hole doping in the antiferromagnetic regime (0 <
Journal
Journal of Superconductivity
Journal Volume
9
Journal Issue
4
Pages
337-342
Date Issued
1996
Author(s)
Johnston, D. C.
Borsa, F.
Carretta, P.
Lascialfari, A.
Gooding, R. J.
Salem, N. M.
Vos, K. J. E.
Cho, J. H.
Torgeson, D. R.
Abstract
The diffusion of the excess oxygen during phase separation in La2CuO4 + δ was studied using thermal history-dependent normal state magnetic susceptibility χ(T, t) measurements versus temperature T and time t as a probe. A large thermal hysteresis of χ(T) was observed for La2CuO4.044 between data obtained after quenching to 5 K and then warming, and data obtained while or after slowly cooling from 300 K. A model for the excess oxygen diffusion is presented, from which the χ(T, t) data yield a T-independent activation energy of 0.24(3) eV for the diffusion coefficient of the excess oxygen from 150 to 220 K. In related work, we have used 139La NQR and μSR measurements to probe the antiferromagnetic (AF) region (x < 0.02) of the La2 - xSrxCuO4 system below the Néel temperature TN(x), from which we extract the Cu+2 staggered magnetization M†(x, T). M†(x, T = 0), extrapolated from above 30 K, was successfully modeled with spin-wave theory, assuming that the doped holes are mobile and are situated in walls in the CuO2 plane which uncouple undoped AF domains; these domains are coupled to those in adjacent CuO2 planes. This agreement supports the previous hypothesis that microsegregation of the (mobile) doped holes into domain walls occurs above ∼30 K, consistent with the phenomenology of Emery and Kivelson. Below ∼30 K, an anomalous increase in M†(x, T) is observed, such that M†(x, T = 0) is nearly independent of x. We interpret this effect as arising from localization of the doped holes below ∼30 K. © 1996 Plenum Publishing Corporation.
SDGs
Publisher
Kluwer Academic/Plenum Publishers
Type
journal article