Sr impurity effects on the magnetic correlations of LaSrCuO

TL;DR

This paper investigates how Sr impurities influence magnetic correlations in LaSrCuO, revealing small AFM clusters, a percolating impurity network, and the emergence of incommensurate correlations around 5% doping, supported by experimental and theoretical analysis.

Contribution

It introduces a theoretical model explaining the magnetic behavior and impurity effects in LaSrCuO, aligning with experimental susceptibility measurements and predicting incommensurate correlations at higher doping.

Findings

Curie constant scales as 1/(2 ξ^2) at zero temperature.

Ground state magnetic correlations are commensurate.

Incommensurate correlations develop around 5% doping.

Abstract

We examine the low-temperature magnetic properties of moderately doped LaSrCuO paying particular attention to the spin-glass (SG) phase and the C-IC transition as they are affected by Sr impurity disorder. New measurements of the low-temperature susceptibility in the SG phase show an increase of an anomalously small Curie constant with doping. This behaviour is explained in terms of our theoretical work that finds small clusters of AFM correlated regions separated by disordered domain walls. The domain walls lead to a percolating sequence of paths connecting the impurities. We predict that for this spin morphology the Curie constant should scale as $1/(2 \xi(x,T=0)^2)$, a result that is quantitatively in agreement with experiment. Also, we find that the magnetic correlations in the ground states in the SG phase are commensurate, and that this behaviour should persist at higher temperatures where the holes should move along the domain walls. However, our results show that incommensurate correlations develop continuously around 5 % doping, consistent with recent measurements by Yamada.