LAUSR

Motivated by recently discovered organic antiferromagnets, we examine an extended triangular lattice that consists of two types of triangles of bonds with exchange coupling constants \(J_{\ell }\) and \(J'_{\ell }\) (\(\ell \) = 1, 2, and 3), respectively. The simplified system with \(J_{\ell } = J'_{\ell } > 0\) is the spatially completely anisotropic triangular lattice (SCATL) antiferromagnet examined previously. The extended system, which we call an extended SCATL (ESCATL), has two different spatial anisotropy parameters J3/J2 and \(J'_{3}/J'_{2}\) when \(J_{1} = J'_{1}\) is assumed. We derive classical phase diagrams and spin structures. It is found that the ESCATL antiferromagnet exhibits two up–up–down–down (uudd) phases when the imbalance of the anisotropy parameters is significant, in addition to the three Neel phases that occur in the SCATL. When the model parameters vary, these collinear phases are continuously connected by the spiral-spin phase. Using the available model parameters for the orga...