Positive zero-field splitting and unexpected slow magnetic relaxation in the magneto-chemical calibrant HgCo(NCS)4.

DC magnetization data for HgCo(NCS)4 confirm positive value of the zero-field splitting D-parameter. High-frequency and -field EPR gave gz = 2.05, gx = 2.16 and D/hc = 5.39 cm-1. The complex exhibits a field-induced slow magnetic relaxation with two relaxation modes and unusual temperature evolution of the relaxation time.