Magnetic Phase Transitions in MII[N(CN)2]2

We summarize the magnetic behavior of MII[N(CN)2]2 (M ˭ Co, Ni, Mn and Zn). Analyses of the DC magnetization and AC susceptibility data demonstrate that α-CoII[N(CN)2]2 (1a) and NiII[N(CN)2]2 (2) are ferromagnets below Tc, while β-CoII[N(CN)2]2 (1b) and MnII[N(CN)2]2 (3) are canted antiferromagnets below TN. ZnII[N(CN)2]2 (4) is diamagnetic. Specific heat and neutron powder diffraction results clearly define the transition temperatures for 1a, 1b, 2 and 3. Crystal structure determination from high-resolution neutron powder data for 1a, 2 and 3 shows that the three systems are isomorphous and crystallize in the orthorhombic space group Pnnm with Z = 2. Single crystal X-ray diffraction shows that 4 crystallizes in the orthorhombic space group Pnma with Z = 4. We solved the magnetic structures of 1a, 2 and 3 from neutron powder diffraction experiments. All low-temperature measurements are consistent with high-spin 1b, 2, 3 and 4, though 1a exhibits an effective J′ = 1/2 behavior.