A complete phase diagram of Zn substituted quantum quasi-two-dimensional helimagnet LiCu2O2 has been presented. Helical ordering transition temperature (T_h) of the original LiCu2O2 follows finite size scaling for less than ~ 5.5% Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution > 5.5% quenches the long-range helical ordering and introduces an intriguing Zn level dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for T_c (Zn > 0.055,H). The magnetic coupling constants of nearest-neighbor (nn) J1 and next-nearest-neighbor (nnn) J2 (alpha=J2/J1) are extracted from high temperature series expansion (HTSE) fitting and N=16 finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin driven multiferroic material.
@article{arxiv.1006.5257,
title = {Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu2O2},
author = {H. C. Hsu and J. -Y. Lin and W. L. Lee and M. -W. Chu and T. Imai and Y. J. Kao and C. D. Hu and H. L. Liu and F. C. Chou},
journal= {arXiv preprint arXiv:1006.5257},
year = {2013}
}