Determination of the magnetic structure of manganese carbodiimide with diffraction experiments using polarized neutrons

The magnetic structure of MnNCN, the nitrogen equivalent of MnO, and the first carbodiimide of a non-d¹⁰ transition metal ever made, has been determined on the basis of spin-polarized neutron-diffraction data close to absolute zero temperature. The S=5/2 moments of the high-spin Mn²⁺ ions lie within the ab hexagonal sheets and exhibit an antiferromagnetic ordering between the sheets along the c axis. Below the Néel point (28 K), a temperature-dependent ordering pattern exists due to magnetic frustration inside the sheets, characterized by a varying angle between the moments. A comparison with other magnetic structures reveals that the compact NCN²⁻ group is capable of mediating significant spin density needed to ensure relatively strong magnetic communication in view of a large Mn²⁺–Mn²⁺ separation.