PAPER - Nature Physics 149 - Electric Field Control of Spin Transport.pdf

LETTERS
Electric field control of spin transport
SANGEETA SAHOO*, TAKIS KONTOS*, JURG¨ FURER, CHRISTIAN HOFFMANN, MATTHIAS GRABER,¨
AUDREY COTTET AND CHRISTIAN SCHONENBERGER¨ †
Institut f¨urPhysik, Universitat¨ Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
*These authors contributed equally to this work
†e-mail: Christian.******@¨
Published online: 23 October 2005; doi:
pintronics aims to develop electronic devices whose In this letter, we report on TMR measurements of MWNTs
resistance is controlled by the spin of the charge carriers and SWNTs that are contacted with ic electrodes and
Sthat flow through them1–3. This approach is illustrated capacitively coupled to a back-gate20. A typical sample geometry
by the operation of the most basic spintronic device, the is shown in the inset of Fig. 1. As a result of resonant tunnelling,
spin valve4–6, which can be formed if two ic we observe a striking oscillatory amplitude and sign modulation
electrodes are separated by a thin tunnelling barrier. In of the TMR as a function of the gate voltage. We have studied
most cases, its resistance is greater when the two electrodes and observed the TMR on nine samples (seven MWNTs and two
are ized in opposite directions than when they are SWNTs) with various tube lengths L between the ic
ized in the same direction7,8. The relative differe