am508173j_si_001.pdf (196.73 kB)
Magnetoresistance Effect in Rubrene-Based Spin Valves at Room Temperature
journal contribution
posted on 2015-03-04, 00:00 authored by Xianmin Zhang, Qinli Ma, Kazuya Suzuki, Atsushi Sugihara, Gaowu Qin, Terunobu Miyazaki, Shigemi MizukamiWe fabricate spin-valve devices with
an Fe3O4/AlO/rubrene/Co stacking structure.
Their magnetoresistance (MR)
effects at room temperature and low temperatures are systemically
investigated based on the measurement of MR curves, current–voltage
response, etc. A large MR ratio of approximately 6% is achieved at
room temperature, which is one of the highest MR ratios reported to
date in organic spin valves. With decreasing measurement temperatures,
we observe that the MR ratios increase because of decrease in spin
scattering, and the width of the MR curves becomes larger owing to
increase in the coercivity of the electrodes at low temperature. A
nonlinear current–voltage dependence is clearly observed in
these organic spin valves. From the measurement of MR curve for the
spin valves with different rubrene layer thickness, we observe that
the MR ratios monotonously decrease with increasing rubrene-layer
thickness. We discuss the spin-dependent transport mechanisms in these
devices based on our experimental results and the present theoretical
analysis. Moreover, we note that the devices exhibit smaller MR ratios
after annealing compared to their counterparts without annealing.
On the basis of atomic force microscopy analysis of the organic films
and device resistances, we deduce that the increase of interface spin
scattering induced by large surface roughness after annealing most
probably leads to reduction in the MR ratios.