Enhanced Magnetism in Heterostructures with Transition Metal Dichalcogenide Monolayers Diem Thi-Xuan Dang Ranjan Kumar Barik Manh-Huong Phan and Lilia M.

2025-04-29 0 0 3.1MB 22 页 10玖币

侵权投诉

Enhanced Magnetism in Heterostructures with

Transition Metal Dichalcogenide Monolayers

Diem Thi-Xuan Dang, Ranjan Kumar Barik, Manh-Huong Phan, and Lilia M.

Woods∗

Department of Physics, University of South Florida, Tampa, Florida 33620, USA

E-mail: lmwoods@usf.edu.

Abstract

Two-dimensional materials and their heterostructures have opened up new possibili-

ties for magnetism at the nanoscale. In this study, we utilize ﬁrst-principles simulations

to investigate the structural, electronic, and magnetic properties of Fe/WSe2/Pt sys-

tems containing pristine, defective, or doped WSe2monolayers. The proximity eﬀects

of the ferromagnetic Fe layer are studied by considering defective and Vanadium-doped

WSe2monolayers. All heterostructures are found ferromagnetic, and the insertion of

the transition metal dichalcogenide results in redistribution of spin orientation and an

increased density of magnetic atoms due to the magnetized WSe2. There is an increase

in the overall total density of states at the Fermi level due to WSe2, however, the

transition metal dichalcogenide may lose its distinct semiconducting properties due to

the stronger than van der Waals coupling. Spin resolved electronic structure proper-

ties are linked to larger spin Seebeck coeﬃcients found in heterostructures with WSe2

monolayers.

Heterostructures (HSTs) composed of ferromagnetic (FM) and heavy metal (HM) ﬁlms

are typical systems employing spin-charge conversion mechanisms for spintronics applica-

tions.1The quality of such devices is controlled by the atomic composition of the interface

arXiv:2210.03817v1 [cond-mat.mtrl-sci] 7 Oct 2022

and its spin-dependent properties. In this context, HSTs with 2D layered materials have be-

come of great interest.2Chemically inert layered materials can improve the interface atomic

sharpness and they provide new ways of property tuning. For example, semiconducting tran-

sition metal dichalcogenides (TMDCs) have strong spin orbit coupling (SOC) which allows

the manipulation of spins via electrical means.3On the other hand, their strong spin photon

coupling enables the control of magnetism with optical methods.4The recent discovery of

FM ordering at room temperature in WS2and WSe2monolayers doped by V atoms5–8has

shown that TMDCs can be eﬀective dilute 2D ferromagnets with robust magnetic states,

which can also be light-tunable.

HSTs with semiconducting TMDC layers oﬀer possibilities for new ways to change and

control magnetic properties, spin transport and spin conversion phenomena through novel

interfacial coupling mechanisms. For example, much enhanced magnetic exchange ﬁelds,

valley splitting, and polarization eﬀects tunable via optical methods have been observed in

WSe2/CrI3HSTs.9–11 Several impressive experimental studies have shown that spin current

generation via thermal gradients across FM/TMDC/HM structures is signiﬁcantly altered

when compared with FM/HM systems. Speciﬁcally, a large enhancement of the voltage

diﬀerence due to the longitudinal spin Seebeck eﬀect in Pt/Ni81Fe19 and Pt/YIG after in-

serting WS2(WSe2) layers has been reported.12–15 It was also found that such an increase is

dependent on the number of layers in the heterostructure, degree of coverage by the TMDC

layers, and quality of the interface. Others have examined spin-dependent transport in

Fe3O4/MoS2/Fe3O4and Co/Al2O3/MoS2junctions.16,17 Spin valves based on spin ﬁltering in

WS2/Co and NiFe/MoS2/NiFe have also been reported.18,19 A gate-tunable magnetic order

in WSe2by changing the occupation of the Se vacancy states are successfully demonstrated20

and computational work investigates the origin of ferromagnetism in complex conﬁgurations

of Se vacancies in V-doped WSe2monolayers.21 The generated Se vacancies play a key role in

the structural change of PdSe2because of the laser-induced phase transformation of layered

PdSe2to metallic phase PdSe2–x.22 Ozyilmaz et. al. suggested that the spin Hall eﬀect in

graphene/TMDC heterostructures may also originate from chalcogenide vacancies.23

In addition to these experimental demonstrations, the theoretical understanding of the

interface properties and coupling mechanisms of FM/TMDC/HM systems must also be ad-

vanced. For example, the changes in the band structure of individual FM, TMDC, and

HM layers calculated from ﬁrst principles can help one understand the overall behavior of

the entire HST. Computed charge transfer, bonding, and interfacial hybridization are also

necessary in order to highlight magnetic proximity eﬀects unique to FM/TMDC/HM HSTs.

Additionally, ﬁrst principles simulations are necessary to reveal spin selection transfer mech-

anisms across doped and defective TMDCs.

In this paper, we present ﬁrst principles simulations of Fe/WSe2/Pt HSTs to elucidate

their basic electronic and magnetic properties for the ﬁrst time. We consider several cases in

which the TMDC is a pristine WSe2, a monolayer with V doping and a monolayer with various

types of vacancies. The interplay between the proximity magnetism from the Fe substrate,

the charge transfer and orbital hybdrization across the WSe2monolayer and the large SOC

eﬀects from the Pt layer leads to a complex picture of interface magnetism. The calculated

band structure, as well as the Fermi surface for each component of the considered HSTs,

are instrumental for the detailed microscopic analysis of the electronic and spin-dependent

behavior across the interface.

Diﬀerent HSTs have been constructed by taking the middle layer as pristine WSe2, as

well as monolayers with V atom substitutional dopants or Se or W vacancies. A side view of

the Fe/Pt HST (taken as a reference) and a HST with a WSe2monolayer inserted in-between

the Fe and Pt layers is shown in Fig. 1a. As part of the Fe/WSe2/Pt HST, we consider a

perfect WSe2monolayer, a monolayer with two Se vacancies - WSe2(VSe–Se), a monolayer

with 3.3% doping of V atoms substituting W atoms – W0.957V0.033Se2, a monolayer with two

Se vacancies and a 3.3% V doping - W0.957V0.033Se2(VSe–Se), and a monolayer containing two

Se and one W vacancies – WSe2(VSe–Se + VW), as shown in Fig. 1b-f.

In each case, the TMDC monolayer is in a 2H conﬁguration. Fe and Pt layers with (001)

Figure 1: (a) Side view of Fe/Pt and Fe/WSe2/Pt HSTs. Top views of the various WSe2

monolayers as part of the Fe/WSe2/Pt HSTs: (b) pristine WSe2(HST2) (c) WSe2(VSe–Se),

a defective monolayer with a pair of Se vacancies (HST3); (d) W0.967V0.033Se2, a defective

monolayer with 3.3% V doping substituting W (HST4); (e) W0.967V0.033Se2(VSe–Se), a defec-

tive monolayer with 3.3% V doping and a pair of Se vacancies (HST5); (f) WSe2(VSe–Se +

VW), a defective monolayer with a pair of Se vacancies and a W vacancy (HST6). The inter-

layer distances are denoted in panel (a), while the electronic spin directions for all atoms of

the monolayers are also shown with arrows upon completing the spin-polarized calculations.

surface termination, have been simulated to create the HSTs having layer thickness 2.804 Å

and 3.926 Å, respectively. For the calculations, a supercell consisting of 6×6Fe unit cells

(108 atoms), 3√3×5unit cells for the perfect monolayer (90 atoms), and 3√2×3√2Pt

unit cells (108 atoms) is constructed. In the case of the reference Fe/Pt HST, the TMDC

monolayer is removed, and for the others, defective and/or doped WSe2are part of each

HST (as shown in Fig. 1).

The formation of the supercells introduces slight strains when compared with the lattice

structures of the individual free-standing constituents. The strain is quantiﬁed using =

Table 1: Basic properties of the considered HSTs from Fig. 1. The strain (%) along

the inequivalent a, b lattice directions with and without the vdW correction is shown for

the layer with the largest shrinkage. The interlayer separations d,d1,d2are also given

with and without vdW interaction. The binding energy is calculated using the expression

Eb=EHST −P

Elayer

i/N, where EHT S is the total energy of the HST, Elayer

iis the total

energy of the ithisolated layer, and Nis the number of atoms in the HST unit cell. The

Bader charge is shown for each layered component of the HSTs. The magnetization per atom

m1,m2,m3corresponds to each layer and Mis the total average magnetization of each HST.

The Bader charges and magnetizations are obtained with the vdW correction taken into the

calculations.

Strain (%) Layer seperation (Å) Eb(meV) Bader charge (e)m1

(µB)

(µB)No vdW vdW No vdW vdW No vdW vdW Fe TMDC Pt

HST1 (a, Fe) -3.428

(b, Fe) -3.411

-3.629

-3.620 d= 1.795 d= 1.787 -416.247 -509.738 4.163 – -4.163 2.579 – -0.058 2.521

HST2 (a, Fe) -2.045

(b, Fe) -3.460

-2.563

-3.800

d1= 2.405

d2= 2.405

d1= 2.284

d2= 2.289 -86.078 -195.852 0.888 0.888 -1.776 2.588 0.014 0.023 2.625

HST3 (a, Fe) -2.300

(b, Fe) -3.601

-2.774

-3.906

d1= 2.363

d2= 2.379

d1= 2.200

d2= 2.279 -87.749 -197.653 2.368 -1.143 -1.226 2.589 0.012 0.018 2.619

HST4 (a. Fe) -1.994

(b, Fe) -3.392

-2.510

-3.731

d1= 2.244

d2= 2.320

d1= 2.143

d2= 2.234 -88.237 -199.307 3.450 -2.796 -1.822 2.589 0.026 0.022 2.637

HST5 (a, Fe) -2.540

(b, Fe) -3.432

-2.717

-3.777

d1= 2.311

d2= 2.282

d1= 2.064

d2= 2.209 -91.638 -201.194 3.562 -1.004 -2.559 2.594 0.040 0.025 2.659

HST6 (a, Fe) -2.255

(b, Fe) -3.358

-2.758

-3.731

d1= 2.180

d2= 2.191

d1= 2.043

d2= 2.120 -98.094 -207.405 4.196 -1.001 -3.195 2.596 0.016 0.025 2.637

aHST −ai

ai×100% (aHST - lattice constant of the HST; ai- lattice constant of the Fe, TMDC,

or Pt layers). In Table 1, we show results for of the Fe layer along the inequivalent aand b

lattice directions, and all data is given in Table S-1 in the Supporting Information. For the

Fe and Pt layers, all values are negative indicating that the lattice has shrunk, and overall

this eﬀect is more pronounced when the vdW interaction is taken into account. On the other

hand, slight stretching along the bdirection and shrinkage along the adirection are found

for all considered WSe2monolayers. Nevertheless, ||does not exceed ∼3.9%.

Interlayer separations for each HST with and without the vdW corrections are also re-

ported in Table 1. Including the vdW interaction in the simulations results in decreased d1,

d2as expected. In fact, the interlayer distances are smaller than the typical vdW separations

(usually 3Å), which is indicative of stronger interactions between the layers. Our results

for the calculated binding energies (with included vdW correction), also given in Table 1,

show that Eb∼ −500 meV for the reference Fe/Pt HST is increased to Eb∼ −200 meV for

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

EnhancedMagnetisminHeterostructureswithTransitionMetalDichalcogenideMonolayersDiemThi-XuanDang,RanjanKumarBarik,Manh-HuongPhan,andLiliaM.WoodsDepartmentofPhysics,UniversityofSouthFlorida,Tampa,Florida33620,USAE-mail:lmwoods@usf.edu.AbstractTwo-dimensionalmaterialsandtheirheterostructureshaveopenedu...

展开>> 收起<<

Enhanced Magnetism in Heterostructures with Transition Metal Dichalcogenide Monolayers Diem Thi-Xuan Dang Ranjan Kumar Barik Manh-Huong Phan and Lilia M..pdf

共22页,预览5页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

Enhanced Magnetism in Heterostructures with Transition Metal Dichalcogenide Monolayers Diem Thi-Xuan Dang Ranjan Kumar Barik Manh-Huong Phan and Lilia M.

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: