Disorder, cluster spin glass, and hour-glass spectra in striped magnetic insulators

TL;DR

This paper models how quenched charge disorder in striped magnetic insulators leads to cluster-glass behavior, which explains the hour-glass magnetic spectra observed in materials like La5/3Sr1/3CoO4, deviating from traditional spin-wave theory.

Contribution

It provides a comprehensive model linking charge disorder-induced frustration to hour-glass spectra, highlighting the role of cluster-glass physics in magnetic excitations.

Findings

Quenched charge disorder causes frustration and cluster-glass behavior.

Cluster-glass physics determines the magnetic spectral weight distribution.

The model explains hour-glass spectra beyond spin-wave theory predictions.

Abstract

Hour-glass-shaped magnetic excitation spectra have been detected in a variety of doped transition-metal oxides with stripe-like charge order. Compared to the predictions of spin-wave theory, these spectra display a different intensity distribution and anomalous broadening. Here we show, based on a comprehensive modelling of these phenomena for La5/3Sr1/3CoO4, how quenched disorder in the charge sector causes frustration, and consequently cluster-glass behavior at low temperatures, in the spin sector. This spin-glass physics, which is insensitive to the detailed nature of the charge disorder, but sensitive to the relative strength of the magnetic inter-stripe coupling, ultimately determines the distribution of magnetic spectral weight and thus causes the hour-glass spectrum.