Ferromagnetic (FM) semiconductors hold great promise for spintronics. However, sustaining FM order at room temperature remains a significant challenge. Conventionally, FM coupling in semiconductors is driven by superexchange, while is suppressed by direct-exchange interactions. The superexchange interactions are relatively weak, typically leading to low-temperature ferromagnetism. Here, we propose a contrasting mechanism that direct-exchange can, instead, promote FM coupling in semiconductors. Utilizing a tight-binding dimer model, we demonstrate that the FM coupling between two magnetic ions is enhanced by direct exchange, but suppressed by superexchange interactions, when one ion has less than half-filled orbitals (e.g., ${\mathrm{d}}^{<5}$) and the other more than half filled (e.g., ${\mathrm{d}}^{>5}$). Based on this mechanism, first-principles calculations predict room-temperature ferromagnetism in a class of double transition-metal compound semiconductors, driven by ${\mathrm{d}}^{<5}\text{−}{\mathrm{d}}^{>5}$ direct-exchange interactions [e.g., ${\mathrm{d}}^3\left(\mathrm{C}{\mathrm{r}}^{3+}\right)-{\mathrm{d}}^8\left(\mathrm{C}{\mathrm{o}}^{+}\right)$ interactions in the ${\mathrm{CrCoCF}}_2$ monolayer]. These findings reveal a general mechanism for achieving room-temperature FM semiconductors, opening a promising avenue for spintronics.

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• Ferromagnetism
• Magnetic coupling
• 2-dimensional systems
• Magnetic systems
• First-principles calculations