High-efficiency spin-filtering and magnetoresistance effects in
supramolecular spin valves
Jing Zeng
a
,
*
, Fang Xie
b
, Ke-Qiu Chen
c
,
**
a
College of Physics and Electronic Engineering, Hengyang Normal University, Hengyang 421002, PR China
b
Physics Science and Engineering Technology College, Yichun University, Yichun 33600 0, PR China
c
Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
article info
Article history:
Received 5 September 2015
Received in revised form
8 November 2015
Accepted 16 November 2015
Available online 22 November 2015
Keywords:
Spin-filtering effect
Magnetoresistive effect
Supramolecular spin valve
abstract
By using nonequilibrium Green's functions in combination with the density functional theory, we
investigate the transport properties of the supramolecular spin valves made of ferrocene and pristine (p-
type or n-type) graphene nanoribbons. The results show that ferrocene adsorption on pristine graphene
nanoribbons gives rise to perfect magnetoresistive effect. While for ferrocene adsorption on p-type
graphene nanoribbons, the perfect magnetoresistive effect disappears but a high-efficiency spin-filtering
effect can be observed. More interestingly, the ferrocene adsorption on n-type graphene nanoribbons
bring about the disappearance of spin polarization effect, and thus spin-filtering and magnetoresistive
effect cannot be observed. Our researches also confirm that the doping type of graphene nanoribbons is a
key factor for obtaining a high-performance supramolecular spintronic device.
© 2015 Elsevier Ltd. All rights reserved.
1. Introduction
Recently, spintronic devices have attracted wide attention due
to their potential applications in logical operations and data storage
[1]. The spintronic devices have been considered to one of the
effective solutions for realizing the new revolution of information
industry. At present, the frontier and hot issue in the field of spin
electronics are the study of single-molecule spintronic devices.
Various single-molecule spintronic devices, such as single-
molecule spin valves [2e6], single-molecule spin filters [7e11],
single-molecule spin field-effect transistors [12,13], single-
molecule spin diode [14], etc., have been studied theoretically
and experimentally. Among them, the single-molecule spin valves
receive more attention.
At present, the single-molecule spin valves in experimental and
theoretical studies are mainly based on sandwich structure model,
namely, ferromagnetic bulk metal/molecule/ferromagnetic bulk
metal [5,7,10,12,14e19]. However, there are many drawbacks in this
model, such as complex interface structure, magnetic bulk
electrodes occupying more circuit space, the interaction between
magnetic metal electrode and molecule, the magnetic interaction
between magnetic metal electrode due to the limitation of mo-
lecular length, etc. In order to solve these problems, a new type of
molecular device, the supramolecular spin valve, is proposed. The
first supramolecular spin valve is successfully prepared by
Urdampilleta et al. [20] By supramolecular interactions, a single-
walled carbon nanotube is laterally coupled to TbPc
2
single-
molecule magnets, and thus a supramolecular spin valve is con-
structed. The result shows that the magnetoresistance (MR) ratio
can reach about 300% [20]. Subsequently, Hong and Kim investi-
gated spin transport mechanisms of this supramolecular spin valve
by applying a simple model, and proposed that the MR effect in this
device is driven by spin-dependent Fano resonance [21]. Though
the experiment about the supramolecular spin valve has made
progress, the theoretical research on the corresponding devices is
rare. In the present work, ferrocene and armchair graphene nano-
ribbon (AGNR) are used to construct supramolecular spin valves,
and thus the corresponding spin transport mechanisms are inves-
tigated. The computational results show that this device can
possess high-efficiency spin-filtering and MR effects, which is
determined by the doping type of AGNR. Our study provides a new
thinking to obtain high-performance supramolecular spintronic
devices.
* Corresponding author.
** Corresponding author.
E-mail addresses: hyzengj@126.com (J. Zeng), keqiuchen@hnu.edu.cn
(K.-Q. Chen).
Contents lists available at ScienceDirect
Carbon
journal homepage: www.elsevier.com/locate/carbon
http://dx.doi.org/10.1016/j.carbon.2015.11.046
0008-6223/© 2015 Elsevier Ltd. All rights reserved.
Carbon 98 (2016) 607e612