Magneto-elastic coupling and unconventional magnetic ordering in triangular multiferroic AgCrS2

TL;DR

This study investigates the magneto-elastic coupling and magnetic ordering in AgCrS2, revealing a first-order phase transition to a ferroelectric and unconventional magnetic state with potential atomic displacement mechanisms.

Contribution

It provides new insights into the magnetic structure and ferroelectricity in AgCrS2, highlighting the role of magneto-elastic effects and contrasting with related compounds.

Findings

AgCrS2 undergoes a first-order transition at 41.6 K to a ferroelectric, antiferromagnetic phase.

The magnetic structure features double ferromagnetic stripes coupled antiferromagnetically.

Ferroelectricity may be driven by atomic displacements due to structural distortion.

Abstract

The temperature evolution of the crystal and magnetic structures of ferroelectric sulfide AgCrS2 have been investigated by means of neutron scattering. AgCrS2 undergoes at TN = 41.6 K a first-order phase transition, from a paramagnetic rhombohedral R3m to an antiferromagnetic monoclinic structure with a polar Cm space group. In addition to being ferroelectric below TN, the low temperature phase of AgCrS2 exhibits an unconventional collinear magnetic structure that can be described as double ferromagnetic stripes coupled antiferromagnetically, with the magnetic moment of Cr+3 oriented along b within the anisotropic triangular plane. The magnetic couplings stabilizing this structure are discussed using inelastic neutron scattering results. Ferroelectricity below TN in AgCrS2 can possibly be explained in terms of atomic displacements at the magneto-elastic induced structural distortion. These results contrast with the behavior of the parent frustrated antiferromagnet and spin-driven ferroelectric AgCrO2.