1210.2549 (B. Bernu et al.)

Exchange energies of Kapellasite from high-temperature series analysis
of the kagome lattice J1-J2-Jd-Heisenberg model    [PDF]

B. Bernu, E. Kermarrec, C. Lhuillier, F. Bert, P. Mendels

We present an analysis of the magnetic susceptibility and specific heat data of Kapellasite (Cu3 Zn(OH)6 Cl2) through high-temperature expansions (HTE) of the J1-J2-Jd-Heisenberg model on the Kagome lattice (up to order 9). Experimental data are reproduced with exchange energies J1 = -12.4(2) K and J_2 = -5.0(8) K and J_d=+14.8(8) K, where J_d is the third neighbor exchange energy across the hexagon. The agreement between theory and experiment is excellent for the spin susceptibility down to 20K. Analysis of the spin specific heat data shows a deficit of 10% of the entropy around 10K. This improved modeling confirms the results of Fak et al, (Phys. Rev Lett. 109, 037208 (2012)) regarding the location of Kapellasite in the cuboc2 phase of the Heisenberg model. The quality and limits of this modeling are discussed.

View original: http://arxiv.org/abs/1210.2549