Kamal K. Saha, Anders Blom, Kristian S. Thygesen, Branislav K. Nikolic
Using the nonequilibrium Green function formalism combined with density
functional theory, we study finite-bias quantum transport in Ni/Gr_n/Ni
vertical heterostructures where $n$ graphene layers are sandwiched between two
semi-infinite Ni(111) electrodes. We find that recently predicted "pessimistic"
magnetoresistance of 100% for $n \ge 5$ junctions at zero bias voltage $V_b
\rightarrow 0$, persists up to $V_b \simeq 0.4$ V, which makes such devices
promising for spin-torque-based device applications. In addition, for parallel
orientations of the Ni magnetizations, the $n=5$ junction exhibits a pronounced
negative differential resistance as the bias voltage is increased from $V_b=0$
V to $V_b \simeq 0.5$ V. We confirm that both of these nonequilibrium effects
hold for different types of bonding of Gr on the Ni(111) surface while
maintaining Bernal stacking between individual Gr layers.
View original:
http://arxiv.org/abs/1201.6279
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