  An antiferromagnetic insulating state has been found in the zigzag
phosphorene nanoribbons (ZPNRs) from a comprehensive density functional theory
calculations. Comparing with other one-dimensional systems, the magnetism in
ZPNRs display several surprising characteristics: (i) the magnetic moments are
antiparallel arranged at each zigzag edge; (ii) the magnetism is quite stable
in energy (about 29 meV/magnetic-ion) and the band gap is big (about 0.7 eV);
(iii) a moderate compressive strain will induce a magnetic to nonmagnetic as
well as semiconductor to metal transition. All of these phenomena arise
naturally due to one unique mechanism, namely the electronic instability
induced by the half-filled one dimensional bands which cross the Fermi level at
around {\pi}/2a. The unusual electronic and magnetic properties in ZPNRs endow
them great potential for the applications in nanoelectronic devices.
