1,2,4-Triazole Complexes, IV

Abstract

Magnetic susceptibility measurements on single crystals of Mn(II)(trz)2(NCS)2 in the temperature range 1.8 - 300 K are reported. The compound has two-dimensional structural and magnetic properties. The data from susceptibility measurements are accounted for by considering the material to be a quadratic-layer, S = 5/2 Heisenberg antiferromagnet. From the comparison of the data with predictions from series expansions the intralayer exchange constant was found to be J/k = -0.25 K. A transition to the antiferromagnetic state is observed at TN = 3.29 K with the b axis being the preferred axis. Magnetization measurements at 1.8 K along the b axis reveal a spin-flop transition at 10.8 kOe. The occurence of a second discontinuity in the magnetization curve at 15.6 kOe is explained by assuming that the spin system goes to the spin-flop state via an intermediate spin arrangement, as is suggested by the presence of tilted MnN6 octahedra. From pulsed-field magnetization measurements at 1.17 K, a saturation field Hc = 74 kOe is found which also leads to J / k = -0.25 K. With the aid of neutron powder diffraction at 1.2 K the magnetic space group was determined to be Apb′a 2′! Preliminary results from heat capacity measurements on the corresponding Fe(II), Co(II), Ni(II) and Cu(II) compounds are reported.