Weak ferromagnetism and glassy state in kappa-(BEDT-TTF)2Hg(SCN)2Br

TL;DR

This study reports the discovery of weak ferromagnetism and a spin-glass state in the organic salt kappa-(BEDT-TTF)2Hg(SCN)2Br, expanding understanding of magnetic phenomena in charge-transfer salts.

Contribution

It provides the first evidence of weak ferromagnetism and spin-glass behavior in this specific organic material, highlighting the role of frustrated spins.

Findings

Weak ferromagnetism observed below 20 K.

Presence of a spin-glass ground state.

Frustrated spins suppress long-range magnetic order.

Abstract

Since the first observation of weak ferromagnetism in the charge-transfer salt kappa-(BEDT-TTF)2-Cu[N(CN)2]Cl [U. Welp et al., Phys. Rev. Lett. 69, 840 (1992)], no further evidence of ferromagnetism in this class of organic materials has been reported. Here we present static and dynamic spin susceptibility measurements on kappa-(BEDT-TTF)2Hg(SCN)2Br revealing weak ferromagnetism below about TWF = 20 K. We suggest that frustrated spins in the molecular dimers suppress long-range order, forming a spin-glass ground state in the insulating phase.