Spin-coherent transport in ferromagnetically contacted carbon nanotubes

Zhao, Bo; Mönch, Ingolf; Vinzelberg, H.; Mühl, Thomas; Schneider, Claus M.

doi:10.1063/1.1471570

Cited by 140 publications

(140 citation statements)

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“…The results depend very strongly on ferromagneticelectrode/CNT interfaces, yielding the net GMR effect of the order of 10 -40%. It should be stressed however that also inverse GMR has been reported of roughly similar magnitude but with negative sign [15,17]. A very surprising data concerning Fe-contacted SWCNT were reported in [16], where a measured GMR effect approached 100%, i.e.…”

Section: Gmr In Carbon Nanotubesmentioning

confidence: 90%

“…Bearing in mind, that nowadays CNT lengths used in electric current measurements, are quite often as short as 200-250 nm, it means that practically electrons travel through nanotubes in a spin-coherent way (no spin flips). Experimental papers concern mostly MWCNTs electrically contacted by cobalt [14,15], but there are also reports on iron [16] and permalloy [17] contacted multi-walled and single wall carbon tubes. The results depend very strongly on ferromagneticelectrode/CNT interfaces, yielding the net GMR effect of the order of 10 -40%.…”

Section: Gmr In Carbon Nanotubesmentioning

confidence: 99%

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Spin‐polarized transport through carbon nanotubes

Krompiewski

2005

Physica Status Solidi (b)

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Published online zzz PACS 85.35. Kt, 81.07.De, Carbon nanotubes (CNT) belong to the most promising new materials which can in the near future revolutionize the conventional electronics. When sandwiched between ferromagnetic electrodes, the CNT behaves like a spacer in conventional spin-valves, leading quite often to a considerable giant magneto-resistance effect (GMR). This paper is devoted to reviewing some topics related to electron correlations in CNT. The main attention however is directed to the following effects essential for electron transport through nanotubes: (i) nanotube/electrode coupling and (ii) inter-tube interactions. It is shown that these effects may account for some recent experimental reports on GMR, including those on negative (inverse) GMR.Copyright line will be provided by the publisher 1 Introduction A particularly challenging class of materials for the future electronics are carbon nanotubes, i.e. graphite sheets rolled up in such a manner that they form very long and thin (in atomic scale) cylinders. Their length can be of the order of several micrometers whereas typical cross-sections of single wall carbon nanotubes (SWCNT) are a few nanometers in diameter, and roughly up to 10 times more for multi-wall carbon nanotubes (MWCNT) . Both the SWCNTs and MWCNTs have been attracting much attention of many researchers since they were discovered [1].It is now clear that the electronics based on conventional semiconducting devices (e.g. silicon technology) has faced fundamental limitations as far as further miniaturization is concerned. The reasons are various, including the fact that the relative amount of surface states -destructive for electronic transport properties -increases rapidly in 2-and 3-dimensional systems when their sizes are being reduced. Likewise, it is predicted that the SiO 2 layer in the MOSFET will be too thin soon (within 10 years or so) to retain its insulating properties [2]. So, there is much interest of physicists, technologists and engineers in new generation nano-scale devices, including molecular ones. The adopted approach is the so-called bottom up philosophy, aiming at designing electronic devices at the molecular level. In contrast to siliconbased devices, the molecular ones (incl. carbon nanotubes, CNT) can successfully cope with the more and more demanding miniaturization requirements without worsening their multi-functional properties. Most probably the CNTs are also good candidates for spintronics applications in view of their unusually long spin diffusion length. It is well-known that electrons can travel through carbon nanotubes up to many hundreds of nanometers, still keeping their momentum and spin orientation. So CNTs are believed to be useful in the near future microelectronics (or molecular electronics) as interconnects, and possibly also as active elements in integrated circuits. Physical properties of the CNTs connected to metallic electrodes depend critically on a quality of CNT/metal junctions, and may evolve with increasing transparencies of the j...

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Section: Gmr In Carbon Nanotubesmentioning

confidence: 90%

Section: Gmr In Carbon Nanotubesmentioning

confidence: 99%

Spin‐polarized transport through carbon nanotubes

Krompiewski

2005

Physica Status Solidi (b)

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“…To illustrate the enormous scientific and technological progress that has been made since carbon nanotubes were discovered it is worth to mention new concepts such as: the room temperature single electron transistor, 1 the ballistic carbon nanotube field-effect transistor 2 or the non-volatile random access memory for molecular computing. 3 Recently several both experimental 4,5,6 and theoretical 7,8,9 papers have been published on spin-dependent electrical transport in ferromagnetically contacted carbon nanotubes in an attempt to test their ability to operate as spintronic devices. It has been found that carbon nanotubes -though intrinsically nonmagnetic-reveal quite a considerable GMR effect.…”

Section: Introductionmentioning

confidence: 99%

Giant magnetoresistance of multiwall carbon nanotubes: Modeling the tube/ferromagnetic-electrode burying contact

Krompiewski

Gutiérrez

2004

Phys. Rev. B

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We report on the giant magnetoresistance (GMR) of multiwall carbon nanotubes with ultra small diameters. In particular, we consider the effect of the inter-wall interactions and the lead/nanotube coupling. Comparative studies have been performed to show that in the case when all walls are well coupled to the electrodes, the so-called inverse GMR can appear. The tendency towards a negative GMR depends on the inter-wall interaction and on the nanotube length. If, however, the inner nanotubes are out of contact with one of the electrodes, the GMR remains positive even for relatively strong inter-wall interactions regardless of the outer nanotube length. These results shed additional light on recently reported experimental data, where an inverse GMR was found in some multiwall carbon nanotube samples.

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“…However, additional effects, such as the anomalous magnetoresistance, can contribute to the observed signal in spin-valves [3,4,5,6]. It seems clear, that despite a number of large responses seen in CNT-based devices [1,7,8,9], one needs to go beyond two terminal structures by realizing multi-terminal devices where non-local measurements are feasible [10]. The non-local measurement in spin-valve devices has been pioneered by Johnson and Silsbee [11] in metallic spin-valves and was further applied to various other systems [12,13,14].…”

mentioning

confidence: 99%

Large oscillating nonlocal voltage in multiterminal single-wall carbon nanotube devices

2008

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We report on the observation of a non-local voltage in a ballistic (quasi) one-dimensional conductor, realized by a single-wall carbon nanotube with four contacts. The contacts divide the tube into three quantum dots which we control by the back-gate voltage Vg. We measure a large oscillating non-local voltage V nl as a function of Vg. Though a classical resistor model can account for a non-local voltage including change of sign, it fails to describe the magnitude properly. The large amplitude of V nl is due to quantum interference effects and can be understood within the scattering-approach of electron transport.PACS numbers: 73.23.Ad,73.63.Fg,73.63.Nm,73.63.Kv,72.80.Rj The recent realization of the spin field-effect transistor in carbon nanotube (CNT) devices [1] demonstrated the ability to control spin transport in a quantum dot (QD) [2]. However, additional effects, such as the anomalous magnetoresistance, can contribute to the observed signal in spin-valves [3,4,5,6]. It seems clear, that despite a number of large responses seen in CNT-based devices [1,7,8,9], one needs to go beyond two terminal structures by realizing multi-terminal devices where non-local measurements are feasible [10]. The non-local measurement in spin-valve devices has been pioneered by Johnson and Silsbee [11] in metallic spin-valves and was further applied to various other systems [12,13,14]. This technique separates spin from charge effects. Recent application of the non-local spin technique in CNTs [10] showed the feasibility and yet tremendous challenge of performing such measurements in low dimensional mesoscopic systems. The hallmark of these measurements is that a positive voltage is measured when the magnetization of the injector and detector electrodes are parallel and a negative only when they are antiparallel. However, it has been reported recently that the four-probe resistance with non-magnetic probes in CNTs can be negative due to interference effects [15]. This suggests that the measurement of the non-local spin transport in mesoscopic systems like CNTs with ferromagnetic contacts should be strongly influenced by quantum interference effects.We report here on measurements of a large non-local voltage V nl in multi-terminal CNT devices (Fig. 1a) in the quantum-dot (QD) regime which changes sign and magnitude as the back-gate voltage is swept. We show that V nl cannot be explained by a classical resistor model. Instead, a quantum approach is required. We also show that in these devices, which have relative transparent contacts with resistances in the range of 10 − 100 kΩ, the magnitude of the oscillating V nl greatly exceeds any nonlocal spin signal.Our devices consist of single-wall CNTs grown by chemical vapor deposition (CVD) and contacted with four probes as shown in Fig 1a. Two middle electrodes are ferromagnetic (F) made of PdNi(20nm)/ Co(25nm)/ Pd(10nm) tri-layer, whereas the two outer probes are normal (N) Pd(40nm) electrodes. A PdNi alloy with 30% Pd is used, because it makes stable contacts to the CNT [1], whi...

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Spin-coherent transport in ferromagnetically contacted carbon nanotubes

Cited by 140 publications

References 19 publications

Spin‐polarized transport through carbon nanotubes

Spin‐polarized transport through carbon nanotubes

Giant magnetoresistance of multiwall carbon nanotubes: Modeling the tube/ferromagnetic-electrode burying contact

Large oscillating nonlocal voltage in multiterminal single-wall carbon nanotube devices

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