Magnetic structure of (C5H12N)CuBr3: origin of the uniform Heisenberg chain behavior and the magnetic anisotropy of the Cu2+ (S = 1/2) ions

Abstract

The magnetic properties and electric polarization of the organic/inorganic hybrid system (C₅H₁₂N)CuBr₃ (C₅H₁₂N = piperidinium) were examined on the basis of density functional theory calculations. The spin exchanges of (C₅H₁₂N)CuBr₃ evaluated by energy-mapping analysis show that its uniform Heisenberg antiferromagnetic chain behavior is not caused by the CuBr₃ chains made up of edge-sharing CuBr₅ square pyramids, but by the two-leg spin ladders resulting from interchain interactions. The magnetic anisotropy of the Cu²⁺ ions in (C₅H₁₂N)CuBr₃ originates largely from the Br⁻ ligands rather than the Cu²⁺ ions. The electric polarization of (C₅H₁₂N)CuBr₃ arises from the absence of inversion symmetry in the crystal structure, and is weakly affected by the magnetic structure.