Contact-induced spin relaxation in Hanle spin precession measurements

Maassen, T.; Vera‐Marun, Ivan J.; Guimarães, Marcos H. D.; Wees, van Bart

doi:10.1103/physrevb.86.235408

Cited by 88 publications

(170 citation statements)

References 39 publications

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“…Complete and abrupt switching between P and AP is observed, enabling determination of DR NL , the T and d dependence of which allow for extraction of a(T) and l N (T). Figure 1d shows the dependence of R P and R AP on H > , for a d ¼ 2 mm Fe/Cu device at T ¼ 50 K. The gradually damped oscillations derive from the Hanle effect 12,23,25,29,36,37,39 (because of the precession of the diffusing spins about H > ), R P and R AP merging at high H > when FM inj and FM det are driven out of plane (see schematics, Fig. 1d).…”

Section: Resultsmentioning

confidence: 99%

“…(This was recorded for positive and negative H >, but we plot here only the symmetric component.) Such large d is used to enable fitting with analytical expressions for spin diffusion-precession (see Methods), with no need to account for back-diffusion of injected spins 23 . The width and amplitude of the oscillations in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Remarkably, despite the maturity of metallic spintronics, there remain large gaps in our fundamental understanding of spin transport in metals, particularly with injection of spins across ferromagnet (FM)/nonmagnetic metal (NM) interfaces, and their subsequent diffusion and relaxation. Unresolved issues include the applicability of the widely employed Elliott-Yafet (E-Y) 3 spin relaxation mechanism [4][5][6][7][8][9][10] , the influence of defects, surfaces and interfaces on spin relaxation at nanoscopic dimensions 8,[11][12][13][14][15] , the importance of magnetic and spin-orbit scattering [16][17][18] and the accuracy of existing models [19][20][21][22][23] .…”

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Kondo physics in non-local metallic spin transport devices

et al. 2014

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The non-local spin-valve is pivotal in spintronics, enabling separation of charge and spin currents, disruptive potential applications and the study of pressing problems in the physics of spin injection and relaxation. Primary among these problems is the perplexing nonmonotonicity in the temperature-dependent spin accumulation in non-local ferromagnetic/ non-magnetic metal structures, where the spin signal decreases at low temperatures. Here we show that this effect is strongly correlated with the ability of the ferromagnetic to form dilute local magnetic moments in the NM. This we achieve by studying a significantly expanded range of ferromagnetic/non-magnetic combinations. We argue that local moments, formed by ferromagnetic/non-magnetic interdiffusion, suppress the injected spin polarization and diffusion length via a manifestation of the Kondo effect, thus explaining all observations. We further show that this suppression can be completely quenched, even at interfaces that are highly susceptible to the effect, by insertion of a thin non-moment-supporting interlayer.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Kondo physics in non-local metallic spin transport devices

et al. 2014

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“…The highly resistive state in those regions would effectively block diffusion toward the non-local detector of the electronic spin, which tends to remain within the (non-encapsulated) regions where the magnetic contacts are located. This scenario leads us to an interesting case of the spin conductivity mismatch problem, 44 where the regions with large and low spin conductance are both contained within the spin transport channel. We note that the spin signal at room temperature is modulated by only~50 %, confirming the interpretation of a strong modulation only when a sizable transport gap is present (Supplementary Figure S6).…”

Section: Spin Transport In Bilayer Graphenementioning

confidence: 99%

Electronic spin transport in dual-gated bilayer graphene

et al. 2016

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The elimination of extrinsic sources of spin relaxation is key to realizing the exceptional intrinsic spin transport performance of graphene. Toward this, we study charge and spin transport in bilayer graphene-based spin valve devices fabricated in a new device architecture that allows us to make a comparative study by separately investigating the roles of the substrate and polymer residues on spin relaxation. First, the comparison between spin valves fabricated on SiO 2 and BN substrates suggests that substrate-related charged impurities, phonons and roughness do not limit the spin transport in current devices. Next, the observation of a fivefold enhancement in the spin-relaxation time of the encapsulated device highlights the significance of polymer residues on spin relaxation. We observe a spin-relaxation length of~10 μm in the encapsulated bilayer, with a charge mobility of 24 000 cm 2 Vs − 1 . The carrier density dependence on the spin-relaxation time has two distinct regimes; no4 × 10 12 cm − 2 , where the spin-relaxation time decreases monotonically as the carrier concentration increases, and n ⩾ 4 × 10 12 cm − 2 , where the spin-relaxation time exhibits a sudden increase. The sudden increase in the spin-relaxation time with no corresponding signature in the charge transport suggests the presence of a magnetic resonance close to the charge neutrality point. We also demonstrate, for the first time, spin transport across bipolar p-n junctions in our dual-gated device architecture that fully integrates a sequence of encapsulated regions in its design. At low temperatures, strong suppression of the spin signal was observed while a transport gap was induced, which is interpreted as a novel manifestation of the impedance mismatch within the spin channel. INTRODUCTIONGraphene is considered to be a promising spin-channel material for future spintronics applications 1 because of its high-electronic mobility, 2 weak spin-orbit coupling 3,4 and a negligible hyperfine interaction. 5,6 The initial spin transport studies were mainly performed on single-layer 7-10 and bilayer exfoliated graphene, 9,11 and large-area graphene 12-15 deposited on conventional SiO 2 substrates. Although enhanced spin-relaxation times have been reported for bilayer graphene-based devices compared with those based on a single layer, the relatively low spin diffusion constants overall yield a lower spin-relaxation length of only 1-2 μm, 9,11 far below the theoretical predictions. 16 One approach suggested for achieving a longer distance spin communication is to increase the spin diffusion constants by fabricating higher mobility devices. 8,17 For charge transport, it has been shown that the carrier mobility of graphene devices on SiO 2 is mainly limited by interfacial charged impurities, surface roughness, and phonons. [18][19][20] The demonstration of an order-of-magnitude improvement in the mobility of graphene encapsulated between atomically flat, charge trap free boron nitride crystals 21,22 has triggered the recent spin transport studies...

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“…The spin diffusion length λ s is determined as 1.35 and 1.14 µm at 30 and 300 K, respectively. Considering these values together with the contact resistance and channel length, our device is within the contact-induced spin relaxation region 27) . In this region, the spin relaxation is dominated by spin absorption at the ferromagnetic electrode and thus makes it difficult for us to perform an accurate evaluation of the spin relaxation in the channel.…”

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confidence: 99%