Anomalous broadening of the spin-flop transition in the reentrant spin-glass phase of La$_{2-x}$Sr$_x$CuO$_4$ ($x=0.018$)

TL;DR

This study investigates the broadening of the spin-flop transition in lightly doped La$_{2-x}$Sr$_x$CuO$_4$, revealing that in the spin-glass phase, the transition becomes broader due to inhomogeneous hole distribution affecting magnetic order.

Contribution

It demonstrates that in the spin-glass phase of La$_{2-x}$Sr$_x$CuO$_4$, the spin-flop transition broadens because of increased spatial variance in hole concentration, a novel insight into magnetic inhomogeneity.

Findings

Spin-flop transition remains finite at low temperatures.

Broadening of the transition correlates with hole distribution inhomogeneity.

Homogeneous antiferromagnetic order is disturbed by hole redistribution.

Abstract

The magnetization in a lightly doped La$_{2-x}$Sr$_x$CuO$_4$ ($x=0.018$) single crystal was measured. Spin-flop transition was clearly observed in the hole doped antiferromagnetically ordered state under increasing magnetic fields perpendicular to the CuO$_2$ plane. In the spin-glass phase below 25K, the spin-flop transition becomes broad but the step in the magnetization curve associated with the transition remains finite at the lowest temperature. We show in this report that, at low temperature, the homogeneous antiferromagnetic order is disturbed by the re-distribution of holes, and that the spatial variance of the local hole concentration around $x=0.018$ increases.