  We present a first-principles theoretical study of electric field-and
strain-controlled intrinsic half-metallic properties of zigzagged aluminium
nitride (AlN) nanoribbons. We show that the half-metallic property of AlN
ribbons can undergo a transition into fully-metallic or semiconducting behavior
with application of an electric field or uniaxial strain. An external
transverse electric field induces a full charge screening that renders the
material semiconducting. In contrast, as uniaxial strain varies from
compressive to tensile, a spin-resolved selective self-doping increases the
half-metallic character of the ribbons. The relevant strain-induced changes in
electronic properties arise from band structure modifications at the Fermi
level as a consequence of a spin-polarized charge transfer between pi-orbitals
of the N and Al edge atoms in a spin-resolved self-doping process. This band
structure tunability indicates the possibility ofdesigning magnetic nanoribbons
with tunable electronic structure by deriving edge states from elements with
sufficiently different localization properties. Finite temperature molecular
dynamics reveal a thermally stable half-metallic nanoribbon up to room
temperature.
