Heisenberg spins on an anisotropic triangular lattice: PdCrO2 under uniaxial stress

TL;DR

This study investigates how uniaxial stress affects the magnetic order of PdCrO2, revealing rapid changes in magnetic periodicity and a first-order transition in magnetic structure, highlighting the material's sensitivity to lattice anisotropy.

Contribution

It provides new insights into the stress-induced magnetic phase transitions and anisotropy effects in a triangular antiferromagnet, using neutron diffraction and resistivity measurements.

Findings

Magnetic order periodicity changes rapidly with applied stress.

No locking of incommensurate magnetic order to a commensurate state observed.

First-order transition from double-q to single-q magnetic structure at ~0.4 GPa.

Abstract

When Heisenberg spins interact antiferromagnetically on a triangular lattice and nearest-neighbor interactions dominate, the ground state is 120$^{\circ}$ antiferromagnetism. In this work, we probe the response of this state to lifting the triangular symmetry, through investigation of the triangular antiferromagnet PdCrO$_2$ under uniaxial stress by neutron diffraction and resistivity measurements. The periodicity of the magnetic order is found to change rapidly with applied stress; the rate of change indicates that the magnetic anisotropy is roughly forty times the stress-induced bond length anisotropy. At low stress, the incommensuration period becomes extremely long, on the order of 1000 lattice spacings; no locking of the magnetism to commensurate periodicity is detected. Separately, the magnetic structure is found to undergo a first-order transition at a compressive stress of $\sim$0.4 GPa, at which the interlayer ordering switches from a double- to a single-q structure.