Finite magnetization plateau from a two-dimensional antiferromagnet: density functional analysis of the magnetic structure of Cu3(P2O6OH)2.

We evaluated the intrachain and interchain spin exchanges of Cu(3)(P(2)O(6)OH) consisting of (Cu2-Cu2-Cu1)(∞) chains by density functional calculations to find that the magnetic properties of Cu(3)(P(2)O(6)OH)(2) are not governed by the J(1)-J(2)-J(2) trimer chain along the c-direction, but by a two-dimensional (2D) antiferromagnetic lattice in which J(1)-J(3)-J(3) trimer chains along the (a-c/2)-direction are interconnected by J(6) monomer chains along the a-direction. Despite its 2D character, Cu(3)(P(2)O(6)OH)(2) shows a 1/3 magnetization plateau because it is a spin-1/2 trimer system with one dominant antiferromagnetic dimer exchange.