The Hour-Glass Magnetic Spectrum Arising from a Striped, Cluster Spin Glass Ground State in La1.75Sr0.25CoO4

TL;DR

This study reveals an hour-glass magnetic excitation spectrum in La1.75Sr0.25CoO4, modeled by a disordered cluster spin glass state, highlighting the role of disorder and quasi-one-dimensional correlations in such spectra.

Contribution

It demonstrates the presence of an hour-glass spectrum in La1.75Sr0.25CoO4 and models it with a disordered spin glass ground state, extending understanding of magnetic excitations in cobaltates.

Findings

Hour-glass magnetic spectrum observed in La1.75Sr0.25CoO4

Spectrum broader than in similar compounds

Supports disordered cluster spin glass ground state

Abstract

We report inelastic neutron scattering results that reveal an hour-glass magnetic excitation spectrum in La1.75Sr0.25CoO4. The magnetic spectrum is similar to that observed previously in La1.67Sr0.33CoO4, but the spectral features are broader. We show that the spectrum of La1.75Sr0.25CoO4 can be modeled by the spin dynamics of a system with a disordered cluster spin glass ground state. Bulk magnetization measurements are presented which support the proposed glassy ground state. The observations reiterate the importance of quasi-one-dimensional magnetic correlations and disorder for the hour-glass spectrum, and suggest that disordered spin and charge stripes exist at lower doping in La2-xSrxCoO4 than previously thought.