Microscopic magnetic modeling for the S=1/2 alternating-chain compounds Na3Cu2SbO6 and Na2Cu2TeO6

作者：Schmitt M^*; Janson O; Golbs S; Schmidt M; Schnelle W; Richter J; Rosner H

来源：Physical Review B, 2014, 89(17): 174403.

DOI：10.1103/PhysRevB.89.174403

The spin-1/2 alternating Heisenberg chain system Na3Cu2SbO6 features two relevant exchange couplings: J(1a) within the structural Cu2O6 dimers and J(1b) between the dimers. Motivated by the controversially discussed nature of J(1a), we perform extensive density-functional-theory (DFT) calculations, including DFT + U and hybrid functionals. Fits to the experimental magnetic susceptibility using high-temperature series expansions and quantum Monte Carlo simulations yield the optimal parameters J(1a) = -217 K and J(1b) = 174 K with the alternation ratio a = J(1a)/J(1b) similar or equal to -1.25. For the closely related system Na2Cu2TeO6, DFT yields substantially enhanced J1b, but weaker J(1a). The comparative analysis renders the buckling of the chains as the key parameter altering the magnetic coupling regime. Numerical simulation of the dispersion relations of the alternating-chain model clarify why both antiferromagnetic and ferromagnetic J(1a) can reproduce the experimental magnetic susceptibility data.

• 出版日期2014-5-2