Ferrimagnetic Order in Tetragonal Antiperovskite Mn3GeN: Article No. 074410

The crystal and magnetic structures of the nitride antiperovskite Mn3GeN reveals ferrimagnetic order stemming from a distorted kagome-derived lattice of the Mn atoms. Polycrystalline Mn3GeN was synthesized via a solid-state reaction and characterized using neutron powder diffraction, dc magnetometry, and first-principles calculations. Rietveld refinement reveals near-stoichiometric composition (Mn3GeN0.992(7)) adopting a tetragonal I4/mcm structure at T=500K and below, featuring axially distorted and tilted [NM n6] octahedra that result in a buckled Mn kagome lattice. On heating, the tetragonal distortion and octahedral tilt angle decrease continuously before transitioning to the cubic Pm3m antiperovskite phase at T~527K. Neutron diffraction and magnetometry together reveal noncollinear ferrimagnetic ordering. For 30K<=T<=500K, the magnetic structure is described by magnetic space group Iba'm' (72.544), with inequivalent Mn1 and Mn2 sublattices that couple antiferromagnetically to yield a net moment. Density-functional theory-based calculations show that the different local moments originate from the bandwidths associated with distinct Mn-N bond lengths. Temperature-dependent refinements reveal distinct differences in the thermal disordering profiles of the Mn1 and Mn2 sublattices. These findings reveal a subtlety in the magnetic and structural behavior of Mn3GeN, highlighting the interplay between structural distortions, magnetic ordering, and electronic structure in kagome-derived antiperovskite materials.