 CRC-Day3 is a single-layer ferromagnetic semiconductor with strong spin lattice coupling and a direct and indirect band gap. It exhibits glassy behavior, negative thermal expansion, and an optical response that indicates it is an indirect and direct band-gap semiconductor. Phononic measurements across its ferromagnetic transition suggest super-exchange mechanisms. This article was authored by L. D. Castro, A. J. Klune, M. O. Yoko-Sook and others.