"Mn3AlN" is Really Mn4N.

ABSTRACT

We investigate the synthesis of antiperovskite "Mn3AlN" using the published synthesis procedure, as well as several new reaction pathways. In each case, only a combination of antiperovskite Mn4N and Mn5Al8 or precursors is obtained. The identity of the obtained antiperovskite phase is unambiguously determined to be Mn4N via synchrotron powder X-ray diffraction (SPXRD), X-ray absorption spectroscopy (XAS), and magnetometry. The experimental results are further supported by thermochemical calculations informed by density functional theory (DFT), which find Mn3AlN to be metastable versus decomposition into Mn and AlN. The DFT-based calculations also predict an antiferromagnetic ground state for Mn3AlN. This directly contradicts the previously reported ferromagnetic behavior of "Mn3AlN". Instead, the observed magnetic behavior is consistent with ferrimagnetic Mn4N. We examine the data in the original publication and conclude that the compound reported to be Mn3AlN is in fact Mn4N.