Probing tunneling spin injection into graphene via bias dependence

Zhu, Tiancong; Singh, Simranjeet; Katoch, Jyoti; Wen, Hua; Belashchenko, Kirill D.; Žutić, Igor; Kawakami, Roland

doi:10.1103/physrevb.98.054412

Cited by 13 publications

(11 citation statements)

References 66 publications

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“…Instead of ideally lattice-matched single-crystalline ferromagnet/Gr structures required for effective spin filtering [37], they confirm the formation of van der Waals heterostructures without such lattice matching where the proximitized graphene itself is a source of spin-polarized carriers [26,36]. While in these experiments Co and NiFe were responsible for effective n-and p-doping of graphene [36], our studies show that even with a single ferromagnet, both n-and p-doping of graphene is possible, which could enable different approaches for designing bias-dependent magnetoresistive effects [25,36,57,58].…”

Section: Discussionsupporting

confidence: 55%

Proximity-induced magnetization in graphene: Towards efficient spin gating

Bosnar,

Lončarić,

Lazić

et al. 2020

Preprint

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Instead of the commonly used chemical doping, it can be more favorable to consider transforming graphene through proximity effects by carefully choosing its adjacent regions. While gate-tunable room-temperature spin-dependent properties could be induced in graphene by magnetic proximity effects from common metallic ferromagnets, this approach is complicated by chemical bonding between a metal and graphene suggesting the need for an intervening buffer layer. However, even with a buffer layer there is still a large energy shift of the Dirac cone in graphene away from the Fermi level. Compared to such a large negative shift and its resulting n-doping when graphene is separated from cobalt by a monolayer h-BN or another layer of graphene, we show that it can be favorable to instead separate graphene by a monolayer of gold or platinum. The resulting proximity induced magnetization is larger, energy shift is somewhat reduced and changes its sign, offering a path for proximity-induced spin polarization in graphene which can be tuned at smaller gate-controlled electric field than for the h-BN buffer layer.

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Section: Discussionsupporting

confidence: 55%

Proximity-induced magnetization in graphene: Towards efficient spin gating

Bosnar,

Lončarić,

Lazić

et al. 2020

Preprint

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“…above-mentioned issue of lacking the ability to reproduce the same FM/graphene tunnel contacts. More studies will need to be conducted to better quantify the spin polarization and understand what extrinsic factors (e.g., bias-dependence) impact the experimental measurements [89][90][91] .…”

Section: Spin Injection Into Graphenementioning

confidence: 99%

2D materials for spintronic devices

2020

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2D materials are attractive for nanoelectronics due to their ultimate thickness dimension and unique physical properties. A wide variety of emerging spintronic device concepts will greatly benefit from the use of 2D materials, leading a better way to manipulating spin. In this review, we discuss various 2D materials, including graphene and other inorganic 2D semiconductors, in the context of scientific and technological advances in spintronic devices. Applications of 2D materials in spin logic switches, spin valves, and spin transistors are specifically investigated. We also introduce the spin-orbit and spin-valley coupled properties of 2D materials to explore their potential to address the crucial issues of contemporary electronics. Finally, we highlight major challenges in integrating 2D materials into spintronic devices and provide a future perspective on 2D materials for spin logic devices.

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“…Given that reversal of spin polarization was reported in Co-graphene devices with both MgO 15,34 and hBN tunnel barriers 13,14,34 for negative injector bias in the range of order 100 mV, we assume that indeed the effective spin polarization g ef f of the tunnel current from Co into graphene has a sign change slightly below the Fermi level, as shown in Fig. 7.…”

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confidence: 94%

Spin field-effect transistor action via tunable polarization of the spin injection in a Co/MgO/graphene contact

Ringer

Rosenauer

Völkl

et al. 2018

Applied Physics Letters

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We fabricated a non-local spin valve device with Co-MgO injector/detector tunnel contacts on a graphene spin channel. In this device, the spin polarization of the injector contact can be tuned by both the injector current bias and the gate voltage. The spin polarization can be turned off and even inverted. This behavior enables a spin transistor where the signal is switched off by turning off the spin injection using the field-effect. We propose a model based on a gate-dependent shift of the minimum in the graphene density of states with respect to the tunneling density of states of cobalt, which can explain the observed bias and gate dependence.Spintronics expands electronics from using only the charge of the electron to also utilizing its spin property 1 . So far, spintronic devices have only been used for data storage, but concepts exist for also building spin based logic circuitry 2-4 . The paradigmatic device, the spin field effect transistor was proposed by Datta and Das in 1990 2 . Here, spins are injected from a ferromagnetic electrode into a non-magnetic channel, and a spin-dependent signal is detected at a second, ferromagnetic electrode. Spins are rotated along the way by a gate-tunable spin-orbit interaction. While this device allows for an all-electric control of spin signals, in contrast to magnetic switching of the electrodes, the channel needs to have strong and tunable spin-orbit interaction and, at the same time, a long spin lifetime. Because of these conflicting requirements, an attempt to fully realize the Datta-Das transistor was only presented more than two decades after the original proposal 5 . On the other hand, when the polarization of spin injection can be manipulated electrically, a transistor device can be realized in a device with long spin lifetime in the channel, such as graphene 6 . Electric tunability of spin injection has been demonstrated in magnetic tunnel junctions 7-11 , or Si based devices 12 . For graphene spintronics, bias-dependent spin polarization, including signal inversion, was reported for hexagonal boron nitride (hBN) 13,14 or MgO 15,16 as a tunnel barrier. In a MoS 2 /graphene heterostructure, a gatedependent suppression of the spin signal was reported 17 . However, no gate-controlled signal inversion was reported for tunneling spin injection in graphene devices.In this work, we report on a gate and bias-tunable spin polarization in a Co/MgO/graphene device. Importantly, the sign of spin polarization can be reversed, and spin injection can even be turned off by gate control, thus enabling a true three-terminal spintronic device. We find that at an elevated negative injector bias U inj , the spin polarization vanishes and afterwards changes sign. At this bias setting, which we call spin neutrality point, both sign and magnitude of spin polarization can be controlled by a voltage V g applied to the back gate of the sample. Fig. 1 shows a schematic picture of the graphene FIG. 1. Sample schematic showing a graphene flake with contacts in the non-local spin valve meas...

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Probing tunneling spin injection into graphene via bias dependence

Cited by 13 publications

References 66 publications

Proximity-induced magnetization in graphene: Towards efficient spin gating

Proximity-induced magnetization in graphene: Towards efficient spin gating

2D materials for spintronic devices

Spin field-effect transistor action via tunable polarization of the spin injection in a Co/MgO/graphene contact

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