Strontium Oxide Tunnel Barriers for High Quality Spin Transport and Large Spin Accumulation in Graphene

Singh, Simranjeet; Katoch, Jyoti; Zhu, Tiancong; Wu, Ryan; Ahmed, Adam; Amamou, Walid; Wang, Dongying; Mkhoyan, K. Andre; Kawakami, Roland

doi:10.1021/acs.nanolett.7b03543

Cited by 24 publications

(20 citation statements)

References 30 publications

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“…[ 107–110 ] Barriers including oxides and boron nitride are introduced to achieve tunnel spin injection. [ 111–113 ] For example, pin‐hole free strontium oxide was grown on graphene as the tunnel barrier, which achieved long spin relaxation time exceeding 1 ns. [ 113 ] Despite this, new routes have been under spotlight.…”

Section: Ferromagnetic 2d Materials and Fm‐gated Heterostructuresmentioning

confidence: 99%

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

Chu

Wang

et al. 2020

Advanced Materials

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The emergence of 2D polarized materials, including ferromagnetic, ferrovalley, and ferroelectric materials, has demonstrated unique quantum behaviors at atomic scales. These polarization behaviors are tightly bonded to the new degrees of freedom (DOFs) for next generation information storage and processing, which have been dramatically developed in the past few years. Here, the basic 2D polarized materials system and related devices’ application in spintronics, valleytronics, and electronics are reviewed. Specifically, the underlying physical mechanism accompanied with symmetry broken theory and the modulation process through heterostructure engineering are highlighted. These summarized works focusing on the 2D polarization would continue to enrich the cognition of 2D quantum system and promising practical applications.

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Section: Ferromagnetic 2d Materials and Fm‐gated Heterostructuresmentioning

confidence: 99%

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

Chu

Wang

et al. 2020

Advanced Materials

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“…A single e-beam lithography pattern of bilayer PMMA/MMA resist combined with multi-angle shadow evaporation was utilized to define an SrO tunnel barrier and 60 nm thick Co electrodes. Details of the device fabrication are provided elsewhere 18 . Subsequently, the spin valve device was spin coated with PMMA and soft baked at 50 °C for 2h in order to prevent damaging the SrO/Co electrodes.…”

mentioning

confidence: 99%

Spin Absorption by In Situ Deposited Nanoscale Magnets on Graphene Spin Valves

et al. 2018

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An in situ measurement of spin transport in a graphene nonlocal spin valve is used to quantify the spin current absorbed by a small (250 nm x 750 nm) metallic island. The experiment allows for successive depositions of either Fe or Cu without breaking vacuum, so that the thickness of the island is the only parameter that is varied. Furthermore, by measuring the effect of the island using separate contacts for injection and detection, we isolate the effect of spin absorption from any change in the spin injection and detection mechanisms. As inferred from the thickness dependence, the effective spin current = 2 ℏ absorbed by Fe is as large as 10 8 A/m 2 . The maximum value of is limited by the resistance-area product of the graphene/Fe interface, which is as small as 3 Ωµm 2 . The spin current absorbed by the same thickness of Cu is smaller than for Fe, as expected given the longer spin diffusion length and larger spin resistance of Cu compared to Fe. These results allow for a quantitative assessment of the prospects for achieving spin transfer torque switching of a nanomagnet using a graphene-based nonlocal spin valve.Graphene is a promising material for lateral spin transport due to its low spin orbit coupling and high carrier mobility, leading to long spin diffusion lengths at room temperature 1,2 . The graphene/ferromagnet (FM) interface has proven to be the bottleneck for achieving high spin lifetimes and high spin injection efficiencies, due to spin absorption by the ferromagnetic contacts 3-13 , the possibility of contact-induced spin relaxation mechanisms other than spin absorption 14 , and the challenge of separating these effects from the spin injection and detection efficiencies of the ferromagnet contacts. Understanding spin relaxation and spin absorption at graphene/FM junctions is also important for technological applications such as all-spin logic, in which the magnetization of a nanomagnet is switched by spin-transfer torque when a pure spin current is absorbed 15 . Despite apparent progress [16][17] , this goal has been challenging to achieve in graphene, which is why an experiment observing the evolution of the absorbed spin current while varying the thickness of the nanomagnet is valuable.In this Letter, we quantify the spin current absorbed by a nanomagnetic island deposited on a nonlocal graphene spin valve. Spin transport measurements are completed in situ while growing the Fe island and the results are interpreted using a 2-D finite-element model. We determine that the effective spin current

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“…On the other hand, all devices reported in Fig. 2 make use of FM outer electrodes except for those with an asterisc [8,16,40,42]. This feature is important because, as shown in panel (b), nearly all devices present a spin diffusion length of the order of the distance between inner and outer electrodes, making the comparison between FoMs of a same set of devices (and therefore between results reported in different papers) inaccurate.…”

Section: Non-magnetic (Nm) Outer Electrodesmentioning

confidence: 99%

“…For each barrier material, results are chronologically sorted. Al2O3 [16,27,28,[34][35][36][37][38]; TiO2 [3,6,33,[38][39][40]; MgO [4,12]; hBN [15,20,41]; a-C [8,31]; SrO [42]; Fluorene [43].…”

Section: Non-magnetic (Nm) Outer Electrodesmentioning

confidence: 99%

Roadmap for the Design of All Ferromagnetic Four-Terminal Spin Valves and the Extraction of Spin Diffusion Length

2021

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Graphene is a promising substrate for future spintronics devices owing to its remarkable electronic mobility and low spin-orbit coupling. Hanle precession in spin valve devices is commonly used to evaluate the spin diffusion and spin lifetime properties. In this work, we demonstrate that this method is no longer accurate when the distance between inner and outer electrodes is smaller than six times the spin diffusion length, leading to errors as large as 50% for the calculations of the spin figures of merit of graphene. We suggest simple but efficient approaches to circumvent this limitation by addressing a revised version of the Hanle fit function. Complementarily, we provide clear guidelines for the design of four-terminal spin valves able to yield flawless estimations of the spin lifetime and the spin diffusion coefficient.

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Strontium Oxide Tunnel Barriers for High Quality Spin Transport and Large Spin Accumulation in Graphene

Cited by 24 publications

References 30 publications

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

Spin Absorption by In Situ Deposited Nanoscale Magnets on Graphene Spin Valves

Roadmap for the Design of All Ferromagnetic Four-Terminal Spin Valves and the Extraction of Spin Diffusion Length

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