In the hexagonal perovskite RbCoCl₃ 1-D antiferromagnetic correlations emerge along Co²⁺ chains below 90 K. At lower temperature complex interchain interactions set in and give rise to (partial) 3-D magnetic order. Below T_N1 = 28 K the spins are aligned parallel to the c-axis, but 1/3 of the chains are uncorrelated from their neighbors. Only below T_N2 = 13 K the system achieves a fully ordered state.
RbCoCl₃ is an excellent material to study the physics of Ising chains. The magnetic structures [1] build an important foundation for the accurate interpretation of the spin dynamics measured in each case [2].

This work was carried out in the groups of PD Dr. Karl Krämer (DCBP) and Prof. Dr. Christian Rüegg (PSI) using the facilities SINQ and SLS at PSI, ISIS (UK), and ILL (F).

References:

1. N. P. Hänni, D. Sheptyakov, M. Mena, E. Hirtenlechner, L. Keller, U. Stuhr, L.-P. Regnault, M. Medarde, A. Cervellino, Ch. Rüegg, B. Normand, K. W. Krämer;
   "Magnetic order in the quasi-one-dimensional Ising system RbCoCl₃"
   Phys. Rev. B, 2021, 103(9), 094424/1-13; doi:10.1103/PhysRevB.103.094424 & arXiv:2102.01099.
2. M. Mena, N. Hänni, S. Ward, E. Hirtenlechner, R. Bewley, C. Hubig, U. Schollwöck, B. Normand, K. W. Krämer, D. F. McMorrow, Ch. Rüegg;
   "Thermal control of spin excitations in the coupled Ising-chain material RbCoCl₃"
   Phys. Rev. Lett., 2020, 124(5), 257201/1-6; doi:10.1103/PhysRevLett.124.257201 & arXiv:1811.07178.