Direct measurement of temporal correlations above the spin-glass transition by coherent resonant magnetic x-ray spectroscopy

TL;DR

This paper demonstrates that resonant magnetic x-ray photon correlation spectroscopy (RM-XPCS) can directly measure long-time temporal correlations in spin glasses, revealing critical slowing down and phase transition dynamics.

Contribution

The study introduces RM-XPCS as a novel experimental technique to directly observe and characterize the dynamical correlations and critical slowing down in spin-glass systems.

Findings

Successfully measured spin orientation fluctuations over 1-1000 seconds.

Observed critical slowing down near the spin-glass transition.

Showed potential for studying other complex disordered systems.

Abstract

In the 1970s a new paradigm was introduced that interacting quenched systems, such as a spin-glass, have a phase transition in which long time memory of spatial patterns is realized without spatial correlations. The principal methods to study the spin-glass transition, besides some elaborate and elegant theoretical constructions, have been numerical computer simulations and neutron spin echo measurements . We show here that the dynamical correlations of the spin-glass transition are embedded in measurements of the four-spin correlations at very long times. This information is directly available in the temporal correlations of the intensity, which encode the spin-orientation memory, obtained by the technique of resonant magnetic x-ray photon correlation spectroscopy (RM- XPCS). We have implemented this method to observe and accurately characterize the critical slowing down of the spin orientation fluctuations in the classic metallic spin glass alloy Cu(Mn) over time scales of 1 to 1000 secs. Our method opens the way for studying phase transitions in systems such as spin ices, and quantum spin liquids, as well as the structural glass transition.