The change of bonding status, typically occurring only in chemical processes, could dramatically alter the material properties. Here, we show that a tunable breaking and forming of a diatomic bond can be achieved through physical means, i.e., by a moderate biaxial strain, in the newly discovered MoN2 two-dimensional (2D) material. Based on first-principles calculations, we predict that as the lattice parameter is increased under strain, there exists an isostructural phase transition at which the N-N distance has a sudden drop, corresponding to the transition from a N-N nonbonding state to a N-N single bond state. Remarkably, the bonding change also induces a magnetic phase transition, during which the magnetic moments transfer from the N(2p) sublattice to the Mo(4d) sublattice, meanwhile the type of magnetic coupling is changed from ferromagnetic to anti-ferromagnetic. We provide a physical picture for understanding these striking effects. The discovery is not only of great scientific interest in exploring unusual phase transitions in low-dimensional systems, but it also reveals the great potential of the 2D MoN2 material in the nanoscale mechanical, electronic, and spintronic applications.
@article{arxiv.1608.05164,
title = {Strain-induced Isostructural and Magnetic Phase Transitions in Monolayer MoN$_2$},
author = {Yao Wang and Shan-Shan Wang and Yunhao Lu and Jianzhong Jiang and Shengyuan A. Yang},
journal= {arXiv preprint arXiv:1608.05164},
year = {2017}
}