Exchange coupling and helical spin order in the triangular lattice antiferromagnet CuCrO₂ using first principles

The magnetic and the electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO₂ are investigated by first-principles through density functional theory calculations within generalized gradient approximations (GGA)+U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and the spin frustration. It is found that CuCrO₂ has a natural two-dimensional characteristic of the magnetic interaction. Using Monte--Carlo simulation, we obtain the N閑l temperature to be 29.9 K, which accords well with the experimental value 24 K. Based on the non-collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with (110) spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to the intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a+b directions each with a screw-rotation angle of about 120?. Our calculations of the density of states show that the spin frustration plays an important role in the change of d--p hybridization, while the spin-orbit coupling has very limited influence on the electronic structure.