Transcript Document

Temperature dependence of resistance in epitaxial Fe/MgO/Fe
magnetic tunnel junctions
Q. L. Ma, S. G. Wang, and X. F. Han
Group M02, State Key Laboratory of Magnetism
Institute of Physics, CAS
The temperature dependence of resistance in parallel (P) and antiparallel (AP) configurations (RP,AP) has been
investigated in epitaxial Fe/MgO/Fe junctions with varying MgO barrier thicknesses tMgO. RAP exhibits a substantial decrease
with increasing temperature for samples with tMgO ranging from 3.0 to 1.5 nm. In contrast, RP is approximately temperature
independent when tMgO =3.0 nm and increases with temperature when tMgO=2.1 and 1.5 nm. A mode based on misalignment of
magnetic moment in the electrodes due to thermal excitations was used to describe this temperature dependent of TMR ratio.
Abstract
(1)
(2)
(a)
(b)
(1) Sketch of MTJ structure and measurement setup (a), HRTEM image (b) of Fe/MgO/Fe trilayers.
(3)
(2) Normalized TMR ratio at 4.2 K in junctions.
(3) Temperature dependence of RA in the P and
AP states for tMgO=1.5 nm, where the lines
are fits based on the model (Formula as follow).
(4) Temperature dependent of the TMR ratio for
junctions with tMgO =3.0, 2.1 and 1.5 nm, where
open points represent experimental data and
solid lines represent fits.
(4)
GP (T )  G [1   P M 1 (T ) M 2 (T )]
0
P
GAP (T )  G [1   AP M 1 (T ) M 2 (T )]
0
AP
G [1   P M M (1  1T )(1   2T )]
TMR  0
1
0
0
3/2
3/2
GAP [1   AP M 1 M 2 (1  1T )(1   2T )]
0
P

0
1
0
2
3/2
3/2
is a material-dependent constant ( M1,2 (T )  M [1  T )] )
0
M 1 denotes saturation magnetizations of two magnetic layers at T=0 K
P,AP includes the proportionality factor relating spin polarization,
magnetization and the local interface effect on the spin-polarized
electron tunneling
0
1,2
3/2
Conclusion RP is reported to increase with temperature in epitaxial magnetic junctions with thin MgO barriers 2.1
and 1.5 nm. The temperature dependence of RP,AP originates from the misalignment of magnetic moments in the
electrodes due to thermal excitations. Conversely, we find that in these epitaxial Fe/MgO/Fe junctions the spin independent
term and spin flip scattering are not significant factors in determining the temperature dependence of RP,AP.
Q. L. Ma et al., Appl. Phys. Lett. 95, 052506 (2009), S. G. Wang et al., Phys. Rev. B. 78, 180411(R) (2008)
This project was supported by MOST, NSFC, and CAS,
and in collaboration with Dr. R. Ward at Oxford University
http://www.m02group.com