Ising-like Magnetism in Quasi-Two-Dimensional Co(NO 3 ) 2 ·2H 2 O.

The appearance of electrically neutral water molecules in the structure of cobalt dinitrate dihydrate, Co(NO 3 ) 2 ⋅2H 2 O, drastically changes its magnetic properties as compared to its waterless counterpart, Co(NO 3 ) 2 . The title compound shows Ising-like behavior reflected in its thermodynamic properties. It experiences long-range antiferromagnetic order at T N = 20.5 K and metamagnetic transition at µ 0 H C = 0.76 T. First-principles calculations produce the values of leading exchange interactions J1 ~ 10 K and J2 ~ 0.5 K and single-ion anisotropy D ~ 1 K which allows us to consider Co(NO 3 ) 2 ⋅2H 2 O as a quasi-two-dimensional magnetic system.