Cobalt nitrides

The cobalt nitride system has been studied in detail using adaptive genetic algorithm and first-principles calculations [1].

Materials synthesis under far-from equilibrium conditions has become an important route for materials design and discovery which can drive systems toward metastable configurations which could possess otherwise unattainable functionality.  Through crystal structure searches using adaptive genetic algorithm, we have explored metastable structures of binary cobalt nitrides for possible candidates for rare-earth free permanent magnets. New structures of Co_nN (n = 3…8) are found to have lower energies than those previously discovered by experiments. Some structures exhibit large magnetic anisotropy energy, reaching as high as 200 μeV per Co atom (or 2.45 MJ/m³) based on first-principles density functional calculation. Our theoretical predictions provide useful insights into a promising system for discovery of new rare-earth free magnets and useful guideline for our experimental partner at University of Nebraska-Lincoln to work on this system.

In the following table, selected structures are listed together with their magnetic properties. All the listed MAE values are either uniaxial (positive) or easy plane anisotropy (negative). Each structure is provided in the format of .cif  by clicking the structure ID.

[1] X Zhao, L Ke, CZ Wang, and KM Ho, Metastable cobalt nitride structures with high magnetic anisotropy for rare-earth free magnets. Physical Chemistry Chemical Physics 18 (46), 31680-31690 (2016).