Enhanced magnetoresistance in graphene spin valve

Iqbal, Muhammad Zahir; Hussain, Ghulam; Siddique, Salma; Iqbal, Muhammad Waqas

doi:10.1016/j.jmmm.2017.01.059

Cited by 23 publications

(12 citation statements)

References 23 publications

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“…The large MR > 80% measured here in the case of a monolayer graphene-based MTJ illustrates the strong impact of hybridization with ferromagnetic electrodes on the extracted spin polarization. For comparison, previous reports of 2D-MTJs with monolayer graphene showed at best MR = 3.4% 4,[17][18][19] , indicating a very large increase of spin signal output with our direct CVD approach to form epitaxial Gr/FM interfaces. While in our experiments the Co is polycrystalline and the spin polarization is averaged over many facets, we expect even higher TMR spin signals to be obtained if ideal situations like the ones depicted in theoretical studies such as ref.…”

Section: Grmentioning

confidence: 61%

“…While the negative sign of the MR is expected due to minority spin filtering 3 , its amplitude is doubled compared to previous studies of monolayer graphene junctions with polycrystalline Ni electrodes (−6%) produced using a similar direct CVD process 27 . It also presents a five-fold to ten-fold improvement compared to junctions fabricated with graphene transfer processes 4,[17][18][19] . In previous experimental studies, it has been demonstrated that graphene layers grown on a ferromagnetic polycrystalline Ni electrode by direct CVD are able to induce a spin filtering effect 5,32 , even when only a monolayer graphene is formed 27 .…”

Section: Resultsmentioning

confidence: 98%

“…While many 2D-based heterostructures can be readily fabricated through exfoliation or wet transfer techniques, these ambient processes usually result in degraded interfaces with reduced spin polarizations. Illustratively, the tunneling magnetoresistance (MR) values obtained for FM/monolayer Gr/FM MTJs structures have so far only reached 3.4%, most probably as a result of these integration issues 4 , 16 – 19 . A solution has been found with direct chemical vapor deposition (CVD) that has shown to provide clean and well-defined interfaces, but its exploration is still at its infancy as it requires the processes to be carefully adapted to each particular system 20 – 23 .…”

Section: Introductionmentioning

confidence: 99%

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Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

et al. 2020

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We report on spin transport in state-of-the-art epitaxial monolayer graphene based 2D-magnetic tunnel junctions (2D-MTJs). In our measurements, supported by ab-initio calculations, the strength of interaction between ferromagnetic electrodes and graphene monolayers is shown to fundamentally control the resulting spin signal. In particular, by switching the graphene/ferromagnet interaction, spin transport reveals magneto-resistance signal MR > 80% in junctions with low resistance × area products. Descriptions based only on a simple K-point filtering picture (i.e. MR increase with the number of layers) are not sufficient to predict the behavior of our devices. We emphasize that hybridization effects need to be taken into account to fully grasp the spin properties (such as spin dependent density of states) when 2D materials are used as ultimately thin interfaces. While this is only a first demonstration, we thus introduce the fruitful potential of spin manipulation by proximity effect at the hybridized 2D material / ferromagnet interface for 2D-MTJs.

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Section: Grmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

et al. 2020

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“…[19][20][21] Theoretically, graphene is predicted as a perfect spin filter due to its unique structure for vertical spin valve junctions. [19][20][21] Theoretically, graphene is predicted as a perfect spin filter due to its unique structure for vertical spin valve junctions.…”

Section: Introductionmentioning

confidence: 99%

Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Iqbal

Siddique

Hussain³

2017

Adv Eng Mater

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The magnetotransport properties of spin valve structure are highly influenced by the type of intervening layer inserted between the ferromagnetic electrodes. In this scenario, spin filtering effect at the interfaces plays a crucial role in determining the magnetoresistance (MR) of such magnetic structures, which can be enhanced by using a suitable intervening layer. Here, the authors investigate the spin filtering effect of the two-dimensional layers such as hexagonal boron nitride (hBN), graphene (Gr), and Gr-hBN hybrid system for modifying the magnetotransport characteristics of the vertical spin valve architectures (Ni/hBN/Ni, Ni/Gr/Ni, and Ni/Gr-hBN/Ni). Compared to graphene, hBN incorporated magnetic junction reveals higher MR and spin polarizations (P) suggesting better spin filtering at the interfaces. The MR for hBN incorporated junction is calculated to be %0.83%, while that of graphene junction it is estimated to be %0.16%. Similar contrast is observed in the 'P' of ferromagnets (FMs) for the two junctions, that is, %6.4% for hBN based magnetic junction and %2.8% for graphene device. However, for Gr-hBN device, the signal not only get inverts, but it also suggests efficient spin filtering mechanism at the FM interfaces. Their results can be useful to comprehend the origin of spin filtering and the choice of non-magnetic spacer for magnetotransport characteristics.

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“…[11][12][13][14][15][16] Apart from the application to lateral SV dealing with in-plane spin transport in a graphene channel, another potential application that is the implementation of graphene as a spacer material in vertical SV has recently become a subject of intense interest. [17][18][19][20][21][22] In development of vertical SV, the achievement of both the low resistance-area (RA) product and large magnetoresistance (MR) ratio is required for the realization of read heads for ultrahigh-density hard disk drives, [23] and magnetic random access memory [5,6] with high-speed operation and low power consumption. However, the current technology Graphene-based vertical spin valves (SVs) are expected to offer a large magnetoresistance effect without impairing the electrical conductivity, which can pave the way for the next generation of high-speed and low-power-consumption storage and memory technologies.…”

mentioning

confidence: 99%

Graphene/Half‐Metallic Heusler Alloy: A Novel Heterostructure toward High‐Performance Graphene Spintronic Devices

Larionov

Попов

et al. 2019

Advanced Materials

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For years graphene has been considered as the most potential material which paves the way to advanced spintronic devices [1][2][3][4][5][6] due to its extraordinary electrical and physical properties. [7][8][9][10] The long spin diffusion length in graphene originated from the weak spin-orbit interaction and high electron mobility have stimulated numerous studies on developing graphene-based lateral spin valve (SV) in the past decade. [11][12][13][14][15][16] Apart from the application to lateral SV dealing with in-plane spin transport in a graphene channel, another potential application that is the implementation of graphene as a spacer material in vertical SV has recently become a subject of intense interest. [17][18][19][20][21][22] In development of vertical SV, the achievement of both the low resistance-area (RA) product and large magnetoresistance (MR) ratio is required for the realization of read heads for ultrahigh-density hard disk drives, [23] and magnetic random access memory [5,6] with high-speed operation and low power consumption. However, the current technology Graphene-based vertical spin valves (SVs) are expected to offer a large magnetoresistance effect without impairing the electrical conductivity, which can pave the way for the next generation of high-speed and low-power-consumption storage and memory technologies. However, the graphene-based vertical SV has failed to prove its competence due to the lack of a graphene/ferromagnet heterostructure, which can provide highly efficient spin transport. Herein, the synthesis and spin-dependent electronic properties of a novel heterostructure consisting of single-layer graphene (SLG) and a half-metallic Co 2 Fe(Ge 0.5 Ga 0.5 ) (CFGG) Heusler alloy ferromagnet are reported. The growth of high-quality SLG with complete coverage by ultrahigh-vacuum chemical vapor deposition on a magnetron-sputtered single-crystalline CFGG thin film is demonstrated. The quasi-free-standing nature of SLG and robust magnetism of CFGG at the SLG/ CFGG interface are revealed through depth-resolved X-ray magnetic circular dichroism spectroscopy. Density functional theory (DFT) calculation results indicate that the inherent electronic properties of SLG and CFGG such as the linear Dirac band and half-metallic band structure are preserved in the vicinity of the interface. These exciting findings suggest that the SLG/CFGG heterostructure possesses distinctive advantages over other reported graphene/ferromagnet heterostructures, for realizing effective transport of highly spin-polarized electrons in graphene-based vertical SV and other advanced spintronic devices.

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Enhanced magnetoresistance in graphene spin valve

Cited by 23 publications

References 23 publications

Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

Spin filtering by proximity effects at hybridized interfaces in spin-valves with 2D graphene barriers

Spin Valve Effect of 2D‐Materials Based Magnetic Junctions

Graphene/Half‐Metallic Heusler Alloy: A Novel Heterostructure toward High‐Performance Graphene Spintronic Devices

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