Detailed magnetic studies on Co(N3)2(4-acetylpyridine)2:: a weak-ferromagnet with a very big canting angle

The magnetic properties of Co(N-3)(2)(4acpy)(2) have been thoroughly reexamined on both powder and well-oriented single crystal samples. This azido-bridged cobalt compound of (4, 4) layer shows a weak-ferromagnetic state below T-C = 11.2 K. The magnetic axes were determined to be along the crystallographic a*, b, and c axes for the monoclinic space group P2(1)/c. The easy axis lies along the b-axis, the canting is along the a*-axis, and the hard axis is along the c-axis. Strong anisotropy due to the oriented moments in the ordered state and/or the single-ion anisotropy of Co2+ exists in the whole temperature range from 2 to 300 K. Below T-C, very big spontaneous magnetization was observed and was attributed to the very big canting angle (150 at 2 K). A possible spin configuration was then proposed to explain the experimental results. The origin of the big spin canting was discussed, and a weak-ferromagnetic approach toward molecular magnets with big spontaneous magnetization was proposed accordingly.