• Lampen-Kelley, P.; Rachel, S.; Reuther, J.; Yan, J.; Banerjee, A.; Bridges, C.; Cao, H.; Nagler, S.; Mandrus, D.: Anisotropic susceptibilities in the honeycomb Kitaev system α-RuCl3. Physical Review B 98 (2018), p. 100403(R)/1-6

Open Accesn Version

The magnetic insulator alpha−RuCl3 is a promising candidate to realize Kitaev interactions on a quasi-two-dimensional honeycomb lattice. We perform extensive susceptibility measurements on single crystals of alpha−RuCl3, including angle dependence of the in-plane longitudinal and transverse susceptibilities, which reveal a unidirectional anisotropy within the honeycomb plane. By comparing the experimental results to a high-temperature expansion of a Kitaev-Heisenberg-Gamma spin Hamiltonian with bond anisotropy, we find excellent agreement with the observed phase shift and periodicity of the angle-resolved susceptibilities. Within this model, we show that the pronounced difference between in-plane and out-of-plane susceptibilities as well as the finite transverse susceptibility are rooted in strong symmetric off-diagonal Gamma spin exchange. The Gamma couplings and relationships between other terms in the model Hamiltonian are quantified by extracting relevant Curie-Weiss intercepts from the experimental data.