Quantum continuum fluctuations in glassy perovskite Ca(Co$_{0.15}$Ru$_{0.85}$)O$_{3}$

TL;DR

This study reveals the coexistence of quantum spin continuum and weak spin glass order in Co-doped CaRuO3, showing persistent uncorrelated spin fluctuations and extreme locality of dynamics near the metal-insulator transition.

Contribution

It provides experimental evidence of quantum continuum fluctuations coexisting with glassy behavior in a perovskite near a metal-insulator transition.

Findings

Quantum spin continuum persists below glass transition temperature.

Dynamic susceptibility scaling indicates extreme locality.

Coexistence of continuum and glassy regimes observed.

Abstract

The quantum spin continuum and classical spin freezing, associated with a glassy state, represent two opposite extremes of a correlated electronic material. Here, we report the coexistence of a quantum spin continuum with a weak spin glass order in Co-doped CaRuO$_{3}$ perovskite near the chemical doping dependent metal-insulator transition boundary. Inelastic neutron measurements on Ca(Co$_{0.15}$Ru$_{0.85}$)O$_{3}$ at low temperature, $T$ = 1.5 K, reveal a continuum spectrum in the $Q-E$ space due to uncorrelated spin fluctuations. This persists across the glass transition at $T_G \simeq$23 K. Furthermore, scaling of the dynamic susceptibility yields a very small scaling coefficient $\alpha$ $\simeq$ 0.1, suggesting extreme locality of the dynamic properties. The experimental results indicate the realization of a narrow regime where the distinction between continuum dynamic behavior and glass-like regimes is reduced.