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

Abstract

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.

Preparation Engineering of Two-Dimensional Heterostructures via Bottom-Up Growth for Device Applications

“…In view of this, the HSs indeed exhibited its potential in the practical applications of spintronics. Recently, Li et al prepared another HS with graphene and half-metallic Heusler alloy (Co 2 Fe­(Ge 0.5 Ga 0.5 )) that possessed capacity for applying in the field of spin valves . Unlike some other HSs, the electronic property of graphene was better maintained in this type of HS, as confirmed by X-ray absorption spectroscopy (Figure j).…”

“…(k,l) Plots for orbital magnetic moment ( m orb ), spin magnetic moment ( m spin ), and total magnetic moment ( m total = m orb + m spin ) of Co (k) and Fe (l) versus mean probing depth (λ p ). Reproduced with permission from ref . Copyright 2020 Wiley-VCH.…”

Half-Metallic Heusler Alloy/MoS2 Based Magnetic Tunnel Junction

“…Besides a proper choice of 2D spacers, search for an ideal spin-polarized electron source is of high importance as well . For that purpose, half-metallic materials have been under consideration for decades including Heusler alloys such as Co 2 MnSi, CoFeMnSi, Co 2 FeAl 1/2 Si 1/2 , and others. − Recently, for the first time, the heterostructure of graphene/half-metallic Co 2 FeGe 1/2 Ga 1/2 Heusler alloy was synthesized . The observation of quasi-freestanding nature of the deposited graphene allowed to preserve the perfect spin polarization of CFGG together with graphene Dirac cone.…”

Электронная Структура Графена На Карбиде Кремния, Интеркалированного Атомами Кремния И Кобальта

“…Эта особенность может быть использована в устройствах магнитной памяти [5]. Другим потенциальным применением подобных интерфейсов является инжекция спин-поляризованных электронов [6]. Для реализации этой возможности материал должен обладать большой величиной спиновой поляризации.…”