Fig. 1: Crystal and magnetic structure of YbCl3.
From: Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice
The monoclinic crystal structure (space group C12/m1) and ordered spin configuration (magnetic space group \(C2^{\prime} /m\)) of YbCl3. The monoclinic structure with a = 6.729 Å, b = 11.614 Å, c = 6.313 Å, and β = 110.6° (at T = 10 K) contains nearly ideal honeycomb lattices of Yb3+ ions (red spheres)61. Within each honeycomb lattice, the Yb3+ sites have nearest-neighbor distances of 3.884 Å and 3.867 Å for the exchanges J and \(J^{\prime}\), respectively, and next-nearest-neighbor distances of 6.729 Å and 6.711 Å for the exchanges J2 and \(J_2^{\prime}\), respectively. The resulting three bond angles for the honeycomb lattice are 120°, 119.97°, and 119.97°. The distance between the honeycomb planes is 6.313 Å, corresponding to an interlayer exchange Jc. For the ideal model (see Eq. (1)), we consider \(J=J^{\prime}\) and \({J}_{2}=J_2^{\prime} ={J}_{c}=0\). The spins are antiferromagnetically aligned within each honeycomb plane and point primarily along the a axis with a small tilt of 5(3)° along the c axis, as described in the text.
