Triangular lattice AF realized experimentally

Experimental Realization of a Spin-1=2 Triangular-Lattice Heisenberg Antiferromagnet
Yutaka Shirata,1 Hidekazu Tanaka,1 Akira Matsuo,2 and Koichi Kindo
Phys. Rev. Lett. 108, 057205 (2012)

Crystal structure of Ba3CoSb2O9. The blue single octahedron is a CoO6 octahedron with a Co2+ ion at
the center, and the face-sharing Sb2O9 double octahedron is shaded ochre. Magnetic Co2þ ions form a regular triangular
lattice in the ab plane. Dotted lines denote the chemical unit cell.