Critical behavior of the metallic triangular-lattice Heisenberg antiferromagnet PdCrO2

TL;DR

This study investigates the critical magnetic behavior of PdCrO2, a layered triangular-lattice antiferromagnet, revealing extended spin correlations and deviations from theoretical predictions in specific heat critical exponents.

Contribution

It provides detailed experimental analysis of critical phenomena in PdCrO2, highlighting the persistence of spin correlations well above the Néel temperature and discrepancies with existing models.

Findings

Critical behavior in specific heat persists over a wide temperature range above TN.

Spin correlations develop at temperatures much higher than TN.

Observed critical exponents for specific heat differ from theoretical predictions.

Abstract

We report physical properties of the conductive magnet PdCrO2 consisting of a layered structure with a triangular lattice of Cr3+ ions (S=3/2). We confirmed an antiferromagnetic transition at TN=37.5K by means of specific heat, electrical resistivity, magnetic susceptibility, and neutron scattering measurements. The critical behavior in the specific heat persists in an unusually wide temperature range above TN. This fact implies that spin correlations develop even at much higher temperature than TN. The observed sub-linear temperature dependence of the resistivity above TN is also attributed to the short-range correlations among the frustrated spins. While the critical exponent for the magnetization agrees reasonably with the prediction of the relevant model, that for the specific heat evaluated in the wide temperature range differs substantially from the prediction.