Frustrated spin-1/2 dimer compound K2Co2(Se O3)3 with easy-axis anisotropy

Magnetic susceptibility, magnetization, and specific-heat measurements under both in-plane and out-of-plane field on K2Co2(SeO3)3 single crystals are reported. The Co dimers in this compound, which are made from face-sharing effective spin-1/2 CoO6 octahedra, sit on the corners of a geometrically frustrating triangular planar lattice. No long-range magnetic ordering is found down to 0.35 K, which, together with the large negative Curie-Weiss temperature obtained from fitting the temperature-dependent magnetic susceptibility, indicates that the system is magnetically frustrated. Analysis of the field and orientation dependence of the magnetic and thermodynamic properties suggests the presence of an easy-axis anisotropy. The magnetic fluctuations present due to geometric frustration are more resistant to an in-plane field than a perpendicular-to-plane field.