Exchange in the linear cuprate antiferromagnets Sr2CuO3 and Ca2CuO3

TL;DR

This paper uses ab initio calculations to determine magnetic exchange interactions in linear cuprate antiferromagnets Sr2CuO3 and Ca2CuO3, aligning theoretical predictions with experimental magnetic properties.

Contribution

It provides detailed quantum chemical calculations of exchange interactions in these materials, offering new insights into their magnetic behavior and temperature dependence.

Findings

Intrachain exchange Ja ≈ -119 meV in both compounds

Interchain exchange Jb is much weaker, -0.28 to -0.52 meV

Neel temperatures correlate with Jb/Ja ratio

Abstract

Ab initio quantum chemical calculations of Heisenberg exchange in linear cuprate antiferromagnets are reported. For Sr2CuO3 I obtain Ja=-119 meV for the intrachain coupling and Jb=-0.28 meV for the interchain coupling. For Ca2CuO3 I find Ja=-119 meV and Jb=-0.52 meV. With these values, recent mean field theory gives the staggered magnetic moments as 0.069 and 0.095 mB, in full agreement with recent experiments. The experimental Neel temperatures are found to be proportional to the ratio Jb/Ja to a high accuracy. This indicates that the isolated chain is an antiferromagnet with vanishing Tn.