Journal
PHYSICAL REVIEW B
Volume 90, Issue 16, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.90.165403
Keywords
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Funding
- Deutsche Forschungsgemeinschaft [FOR-912]
- European Union [604391]
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By successive oxygen treatments of graphene nonlocal spin-valve devices we achieve a gradual increase of the contact-resistance-area products (R(c)A) of Co/MgO spin injection and detection electrodes and a transition from linear to nonlinear characteristics in the respective differential dV-dI curves. With this manipulation of the contacts, both spin lifetime and the amplitude of the spin signal can significantly be increased by a factor of seven in the same device. This demonstrates that contact-induced spin dephasing is the bottleneck for spin transport in graphene devices with small R(c)A values. With increasing R(c)A values, we furthermore observe the appearance of a second charge neutrality point (CNP) in gate-dependent resistance measurements. Simultaneously, we observe a decrease of the gate voltage separation between the two CNPs. The strong enhancement of the spin-transport properties as well as the changes in charge transport are explained by a gradual suppression of a Co-graphene interaction by improving the oxide barrier during oxygen treatment.
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