M. S. Grbić, M. Horvatić, S. Krämer, C. Berthier, H. Tanaka
By $^{63,65}$Cu nuclear magnetic resonance (NMR) in magnetic field up to 30 T we study the microscopic properties of the 12-site "pinwheel" valence bond solid state in Rb$_2$Cu$_3$SnF$_{12}$. We find evidence of a strong transverse staggered spin polarization existing in the ground state. The temperature and field dependence of the local hyperfine fields, i.e. the spin polarizations, points to a strong anisotropy of the exchange interactions. This is furthermore corroborated by the field dependence of the singlet-triplet gap \Delta (H), which does not close at some critical field, but is only lowered to a large residual value $\approx$ \Delta (0)/2, and rises again at higher fields. No evidence of a phase transition was detected down to 1.5 K.
View original:
http://arxiv.org/abs/1211.1443
No comments:
Post a Comment