Chlorine NMR in CsCoCl3 and CsMnCl3 and ESR in CsMg(Co)Cl3

Analysis of the 35Cl NMR in single crystals of CsMgCl3, CsMnCl3 at 300°K and of CsCoCl3 at different temperatures yielded the chlorine quadrupole coupling and for the latter two compounds the paramagnetic shift tensors. We found at 300°K: for CsMgCl3, νQ = 4.465 Mc/sec, η = 0.235; for CsMnCl3, νQ = 5.2645 Mc/sec, η = 0.2683 (bent bridge), νQ = 9.1835 Mc/sec, η = 0.0234 (linear bridge); for CsCoCl3, νQ = 6.87925 Mc/sec, η = 0.4293. From the ESR spectrum of CsMg(Co)Cl3, the g and hyperfine tensors were determined (g‖ = 7.37, g⊥ = 2.51, A‖(Co) = 339 × 10−4cm−1, A⊥(Co) = 21 × 10−4cm−1). Using these data and Dq = 660 cm−1, EP = 12 000 cm−1 inferred from the optical spectrum, the spin expectation values 〈S‖〉 and 〈S⊥〉 were calculated for CsCoCl3. The following superhyperfine constants parallel (A‖) and perpendicular (A⊥) to the Me–Cl bond are computed from the measured paramagnetic shifts: A‖ = 1.59, A⊥ = 1.40 (CsMnCl3, ClI, linear bridge), A‖ = 1.68, A⊥ = 1.70 (CsMnCl3, ClII, bent bridge), A‖ = 4.74, A⊥ = 1.65 (CsCoCl3), all in units 10−4 cm−1. No transition to the ordered magnetic state has been observed for CsMnCl3 for temperatures down to 20°K, contrary to ESR data in the literature.