Prediction of monolayer FeP4 with intrinsic half-metal ferrimagnetism above room temperature

The design of high-temperature ferrimagnetic materials is highly demanded for next-generation functional spintronic devices. Here, we propose that the combination of nonmetallic structural units and magnetic atoms is an effective way to achieve high-temperature magnetism in two-dimensional (2D) materials. The predicted $\mathrm{Fe}{\mathrm{P}}_{4}$ monolayer, consisting of quasisquare ${\mathrm{P}}_{4}$ units, shows intrinsic half-metal ferrimagnetism above room temperature. Each Fe atom is coordinated with four P atoms associated with the surrounding four quasisquare ${\mathrm{P}}_{4}$ units. First-principles calculations suggest that the $\mathrm{Fe}{\mathrm{P}}_{4}$ monolayer presents a Curie temperature of 460 K. More interestingly, the itinerant electrons and the unique quasisquare ${\mathrm{P}}_{4}$ units act as intermediaries and play an important role in promoting the Ruderman-Kittel-Kasuya-Yosida and superexchange interactions, respectively, which induces a robust ferrimagnetism. Our findings not only shed light on the promising future of 2D magnetic materials, but also are of interest for high-temperature spintronic applications.