  Seminal Goodenough-Kanamori-Anderson (GKA) rules provide the inceptive
understanding of the superexchange interaction of two magnetic metal ions
bridged with an anion, and suggest fostered ferromagnetic interaction for
orthogonal bridging bonds. However, there are no examples of two-dimensional
(2D) materials with structure that optimizes the GKA arguments towards enhanced
ferromagnetism and its critical temperature. Here we reveal that an ideally
planar GKA ferromagnetism is indeed stable in selected tetragonal
transition-metal xenes (tTMXs), with Curie temperature above 300~K found in CrC
and MnC. We provide the general orbitally-resolved analysis of magnetic
interactions that supports the claims and sheds light at the mechanisms
dominating the magnetic exchange process in these structures. With recent
advent of epitaxially-grown tetragonal 2D materials, our findings earmark tTMXs
for facilitated spintronic and magnonic applications, or as a desirable
magnetic constituent of functional 2D heterostructures.
