Enhanced magnetoresistance in self-assembled monolayer of oleic acid
molecules on Fe3O4 nanoparticles
S. Wang1, F. J. Yue1, D. Wu1, F. M. Zhang1, W. Zhong1 and Y. W. Du 1
1
Nanjing National Laboratory of Microstructures and Department of Physics, Nanjing
University, 22 Hankou Road, Nanjing, China
Spin transport through molecules is investigated using self-assembled monolayers
(SAMs) of oleic acid molecules on half metallic Fe3O4 nanoparticles.[1] Fourier transform
infrared spectroscopy (FTIR) measurements indicate that one monolayer molecules
chemically bonds to the Fe3O4 nanoparticles and the physically absorbed molecules do not
exist in the samples. The magnetoresistance (MR) of cold-pressed, molecule fully covered
nanoparticles is up to 7.3% at room temperature and 17.5% at 115 K under a field of 5.8 kOe,
shown in Fig. 1. And the MR ratio is more than two times larger than that of pure Fe3O4
nanoparticles, suggesting a weaker spin scattering in molecules. The samples show reduced
interparticle resistance, hysteresis I-V curves, and logρ ∼ Τ−1/4 relation of resistivity as a
function of temperature, suggesting the carriers hop through oleic acid molecules, shown in
Fig. 2. These results show that small molecules are promising for development of future spinbased molecular electronics.
This work was supported by the National Basic Research Program of China
(2007CB925104), NSFC (10804046) and Jiangsu NSF (BK2008256).
[1] S. Wang, et al., Appl. Phys. Lett. 94, 012507 (2009).
11
115 K
MR (%)
-4
-8
-12
pure Fe3O4
-16
-20
half coated
fully coated
-6000 -4000 -2000
0
2000 4000 6000
Magnetic Field (Oe)
Fig. 1. MR for pure Fe3O4, half monolayer
molecule coated Fe3O4 and molecule fully
coated Fe3O4, respectively.
10
10
10
9
10
8
10
7
10
6
10
5
10
4
10
ρ (Ω cm)
0
pure Fe3O4
half coated
fully coated
0.25
0.30
-1/4
T
-1/4
0.35
0.40
(K )
Fig. 2. Resistivity as a function of T−1/4 for
pure Fe3O4, half monolayer oleic acid coated
Fe3O4 and molecule fully coated Fe3O4,
respectively.