Channeling the exchanges of eg electrons by Co-implantation for magnetism enhancement in CrI3 monolayer

In recent few years, the two-dimensional (2D) magnets have emerged as one of the most important frontiers in materials physics and attracted much attention. As one of the earliest experimentally discovered 2D magnets, CrI3 shows a wealth of properties and has been extensively studied. In particular, an intriguing characteristic of the CrI3 monolayer is its octahedrally coordinated hollow within the unit-cell, which enables the implantation of a magnetic atom, thereby resulting in an artificial 2D superlattice with fertile physics to explore. In this work, using first-principles calculations, we investigate the Co-implanted CrI3 monolayer, denoted as Co-(CrI3)2, and demonstrate the vital roles of the exchange channels of eg electrons in enhancing magnetism. It is shown that the Co-(CrI3)2 monolayer has a half-metallic ferrimagnetic (FiM) ground-state with a net in-plane magnetic moment of 5.0μB/f.u. and a relatively high Curie point (TC) of ∼195 K, noting that TC of pristine CrI3 is only 45–61 K. The FiM ordering is established by the strong anti-ferromagnetic coupling in the t2g-eg exchange channels of the nearest-neighbor (NN) Cr–Co pair and the sizeable ferromagnetic coupling of the third NN Cr–Cr pair mediated by the itinerant eg electrons. In addition, an in-plane biaxial tensile strain of ∼2% may further enhance TC up to ∼210 K. This work offers unique insights into the magnetism enhancement of the CrI3 monolayer by atom-implantation, paving the way for the development of 2D magnets.