The penta-hexa silicene: A promising candidate for intrinsic room temperature magnetic semiconductor

Performing ab initio calculations, we investigate electronic and magnetic properties of a silicon allotrope (PH-silicene) composed entirely by six silicon pentagons and two silicon hexagons. The dynamically and mechanically stable PH-silicene hosts two-dimensional honeycomb spin structures, which can be antiferromagnetic, ferromagnetic, or ferrimagnetic depending on the applied tensile strain and/or number of stacked layers. In particular, the transition temperature of an in-plane antiferromagnetic ground state and a strain-induced ferromagnetic state of monolayer PH-silicene is found to be around 533 and 80 K, respectively. This unusual metal-free magnetism can be explained by the d(0) charge transfer mechanism. On the other hand, we show that the PH-silicene is an indirect semiconductor with the bandgap of 0.585 eV. When stacking up to 4-layers, they vary from the semiconductor, the semimetal to the normal metal. Our findings suggest PH-silicene as a promising candidate for the room temperature magnetic semiconductor and will pave a way for silicon based spintronic devices.