Magnetic relaxation in a Co(II) based quasi-one dimensional Ising spin system

Single crystal study of Co(NCS)2(aniline)2 reveals that this compound orders at 6.49 K into a canted AF magnetic structure that explains the presence of a hysteresis loop along the b crystal direction. Effective s = 1/2 spins of Co(II) ions within the ground state doublet create an Ising spin system that can be described by J1-J2 triangular model. Temperature dependence of specific heat yields exchange interactions J1 = 31.3(4) K and 2J2 = -2.23(7) K. Applying magnetic field & SIME;6 kOe perpendicular to b compensates for the AF exchange J2 decoupling ferromagnetic spin chains. This restores the one-dimensionality of the system and allows for observation of magnetic relaxation of single chains, similar to previously studied pyridine-based Co(NCS)2L2 compounds. The analysis of the relaxation time is performed taking into account single-ion relaxation mechanisms together with the Glauber relaxation. We also show, using Monte Carlo calculations of specific heat, that for ferromagnetic J1 & drangbrac; |J2|, the triangular Ising model can be approximated by the rectangular Ising model for which the analytical Onsager's solution is available.