We demonstrate that one of the most commonly used criteria to ascertain that tunneling is the dominant conduction mechanism in magnetic tunnel junctions—fits of current–voltage (I–V) data—is far from reliable. Using a superconducting electrode and measuring the differential conductance below Tc, we divide samples into junctions with an integral barrier and junctions having metallic shorts through the barrier. Despite the clear difference in barrier quality, equally reasonable fits to the I–V data are obtained above Tc. Our results further suggest that the temperature dependence of the zero-bias resistance is a more solid criterion, which could therefore be used to rule out possible pinholes in the barrier.

1.
J. S.
Moodera
,
L. R.
Kinder
,
T. M.
Wong
, and
R.
Meservey
,
Phys. Rev. Lett.
74
,
3273
(
1995
).
Google Scholar
 
2.
J. M.
Daughton
,
J. Appl. Phys.
81
,
3758
(
1997
).
Google Scholar
 
3.
W. J.
Gallagher
,
S. S. P.
Parkin
,
Y.
Lu
,
X. P.
Bian
,
A.
Marley
,
K. P.
Roche
,
R. A.
Altman
,
S. A.
Rishton
,
C.
Jahnes
, and
T. M.
Shaw
,
J. Appl. Phys.
81
,
3741
(
1997
).
Google Scholar
 
4.
Y.
Ando
,
H.
Kameda
,
H.
Kubota
, and
T.
Miyazaki
,
Jpn. J. Appl. Phys., Part 2
38
,
L737
(
1999
).
Google Scholar
 
5.
N.
Garcı́a
,
M.
Muñoz
, and
Y.-W.
Zhao
,
Phys. Rev. Lett.
82
,
2923
(
1999
).
Google Scholar
 
6.
G.
Tatara
,
Y.-W.
Zhao
,
M.
Muñoz
, and
N.
Garcı́a
,
Phys. Rev. Lett.
83
,
2030
(
1999
).
Google Scholar
 
7.
C. B. Duke, Tunneling in Solids (Academic, New York, 1969), p. 90.
8.
Tunneling Phenomena in Solids, edited by E. Burnstein and S. Lundqvist (Plenum, New York, 1969).
9.
E. Merzbacher, Quantum Mechanics (Wiley, New York, 1997).
10.
J. G.
Simmons
,
J. Appl. Phys.
34
,
1793
(
1963
).
Google Scholar
 
11.
W. F.
Brinkman
,
R. C.
Dynes
, and
J. M.
Rowell
,
J. Appl. Phys.
41
,
1915
(
1970
).
Google Scholar
 
12.
D. A. Rabson, B. J. Jönsson-Åkerman, R. Escudero, C. Leighton, S. Kim, and Ivan K. Schuller, J. Appl. Phys. (submitted).
13.
A.
Zehnder
,
Ph.
Lerch
,
S. P.
Zhao
,
Th.
Nussbaumer
,
E. C.
Kirk
, and
H. R.
Ott
,
Phys. Rev. B
59
,
8875
(
1999
).
Google Scholar
 
14.
A. F.
Andreev
,
Sov. Phys. JETP
19
,
1228
(
1964
).
Google Scholar
 
15.
G. E.
Blonder
,
M.
Tinkham
, and
T. M.
Klapwijk
,
Phys. Rev. B
25
,
4515
(
1982
).
Google Scholar
 
16.
S. K.
Upadhyay
,
A.
Palanisami
,
R. N.
Louie
, and
R. A.
Buhrman
,
Phys. Rev. Lett.
81
,
3247
(
1998
).
Google Scholar
 
17.
R. J.
Soulen
,
J.
Byers
,
M. S.
Osofsky
,
B.
Nadgomy
,
T.
Ambrose
,
S. F.
Cheng
,
P.
Broussard
,
C. T.
Tanaka
,
J.
Nowak
,
J. S.
Moodera
,
A.
Barry
, and
J. M. D.
Coey
,
Science
282
,
85
(
1998
).
Google Scholar
 
18.
P. M.
Tedrow
and
R.
Meservey
,
Phys. Rep.
238
,
173
(
1997
).
Google Scholar
 
19.
P.
Xiong
,
G.
Xiao
, and
R. B.
Laibowitz
,
Phys. Rev. Lett.
71
,
1907
(
1993
).
Google Scholar
 
20.
P. S.
Westbrook
and
A.
Javan
,
Phys. Rev. B
59
,
14606
(
1999
).
Google Scholar
 
21.
Some nanocontacts were of a less transmissive nature, which made the spin polarization determination not as straightforward.
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