  Coherent spin transport through bilayer graphene (BLG) nanoflakes sandwiched
between two electrodes made of single-layer zigzag graphene nanoribbon was
investigated by means of Landauer-Buttiker formalism. Application of a magnetic
field only on BLG structure as a channel produces a perfect spin polarization
in a large energy region. Moreover, the conductance could be strongly modulated
by magnetization of the zigzag edge of AB-stacked BLG, and the junction,
entirely made of carbon, produces a giant magnetoresistance (GMR) up to
$10^6\%$. Intestinally, GMR and spin polarization could be tuned by varying BLG
width and length. Generally, MR in a AB-stacked BLG strongly increases
(decreases) with length (width).
