Systematic Study of Short Range Antiferromagnetic Order and The Spin-Glass State in Lightly Doped La2-xSrxCuO4

TL;DR

This study systematically investigates the magnetic properties of lightly doped La2-xSrxCuO4, revealing spin-glass behavior and inhomogeneous hole distribution, and proposes a revised magnetic phase diagram based on susceptibility measurements and neutron scattering data.

Contribution

It provides new insights into the magnetic phase diagram and spin-glass behavior in lightly doped La2-xSrxCuO4, highlighting the universal scaling of the spin-glass order parameter and the inhomogeneous hole distribution.

Findings

Spin-glass transition temperatures decrease with doping.

Universal scaling of the spin-glass order parameter.

Correlation between out-of-plane susceptibility deviations and neutron scattering results.

Abstract

Systematic measurements of the magnetic susceptibility were performed on single crystals of lightly doped La2-xSrxCuO4 (x=0.03, 0.04 and 0.05). For all samples the temperature dependence of the in-plane magnetic susceptibility shows typical spin-glass features with spin-glass transition temperatures Tg of 6.3K, 5.5K and 5.0K for x=0.03, 0.04 and 0.05, respectively. The canonical spin-glass order parameter extracted from the in-plane susceptibility of all the samples follows a universal scaling curve. On the other hand, the out-of-plane magnetic susceptibility deviates from Curie law below a temperature Tdv, higher than Tg. Comparing with previous neutron scattering results with an instrumental energy resolution of 0.25 meV from Wakimoto et al., the x-dependence of Tdv is qualitatively the same as that of Tel, the temperature below which the elastic magnetic scattering develops around (pi, pi). Thus, a revised magnetic phase diagram in the lightly doped region of La2-xSrxCuO4 is proposed. The Curie constants calculated from the in-plane susceptibility are independent of the Sr concentration. On the basis of the cluster spin-glass model, this fact might reflect an inhomogeneous distribution of doped holes in the CuO2 plane, such as in a stripe structure.