Disorder driven cluster glass state in a geometrically frustrated hexagonal perovskite

TL;DR

This paper reports the discovery of a cluster glass state in a geometrically frustrated double perovskite, driven by anti-site disorder and complex magnetic interactions, with evidence from structural, magnetic, and transport measurements.

Contribution

It introduces a new example of a disorder-driven cluster glass state in a geometrically frustrated perovskite ruthenate, highlighting the role of anti-site disorder and competing interactions.

Findings

Presence of glassy magnetic behavior with aging and memory effects

Short-range magnetic correlations persist up to room temperature

Global spin freezing occurs around 43 K

Abstract

We report the observation of cluster glass-like properties in a double perovskite ruthenate Ba$_2$CoRuO$_6$ through structural (neutron and synchrotron X-ray diffraction), magnetic and transport measurements. The system exhibits classic glassy characteristics like a frequency dependence in ac Susceptibility, aging and memory effects along with persistance of short-range correlations upto room temperature. The significant ($\sim30\%$) anti-site disorder on the dimer sites, coupled with the inherent geometrical frustration, allows a variety of exchange (both antiferro- and ferromagnetic) interactions to be distributed randomly across the lattice. On cooling, locally dominant interactions cause spins to nucleate and form local, short-range ordered clusters which grow in size until a global freezing occurs at about $T_f \sim 43K$.