  The search for half-metals and spin-gapless semiconductors has attracted
extensive attention in material design for spintronics. Existing progress in
such a search often requires peculiar atomistic lattice configuration and also
lacks active control of the resulting electronic properties. Here we reveal
that a boron-nitride nanoribbon with a carbon-doped edge can be made a
half-metal or a spin-gapless semiconductor in a programmable fashion. The
mechanical strain serves as the on/off switches for functions of half-metal and
spin-gapless semiconductor to occur. Our findings shed light on how the edge
doping combined with strain engineering can affect electronic properties of
two-dimensional materials
