Thermal magnetization fluctuations in tunneling magnetoresistive heads with track width of 100nm have been studied through high-frequency magnetic noise measurement as a function of both transverse and longitudinal fields. The study suggests that in the dynamic region of the heads, the related power spectral density is determined by the magnetization fluctuations of the free layer. At high fields which drive the sensor to the magnetization saturation, an “abnormal” resonance with substantially high amplitude in comparison with that of the free layer is observed when the magnetization of the free layer is nearly antiparallel to that of the reference layer. This abnormal resonance is excluded from the spin torque effect. The detailed analysis suggests that this resonance is due to the magnetization fluctuations in the reference/pinned layers.

1.
N.
Smith
,
J. A.
Katine
,
J. R.
Childress
, and
M. J.
Carey
,
IEEE Trans. Magn.
42
,
114
(
2006
).
2.
K. B.
Klaassen
,
J. V.
Peppen
, and
X. Z.
Xing
,
IEEE Trans. Magn.
42
,
108
(
2006
).
3.
J. G.
Zhu
,
Y. C.
Zhou
, and
S. N.
Mao
,
IEEE International Magnetics Conference
,
2006
(unpublished), DD-03.
4.
N.
Smith
and
P.
Arnett
,
Appl. Phys. Lett.
78
,
1448
(
2001
).
5.
K. B.
Klaassen
,
X. Z.
Xing
, and
J. V.
Peppen
,
IEEE Trans. Magn.
41
,
2307
(
2005
).
6.
Y. C.
Zhou
,
J. G.
Zhu
, and
N.
Kim
,
J. Appl. Phys.
93
,
8579
(
2003
).
7.
O.
Heinonen
and
H. S.
Cho
,
IEEE Trans. Magn.
40
,
2227
(
2004
).
8.
S. N.
Mao
 et al.,
IEEE Trans. Magn.
42
,
97
(
2006
).
9.
J. C.
Slonczewski
,
Phys. Rev. B
39
,
6995
(
1989
).
10.
J. G.
Zhu
,
IEEE Trans. Magn.
35
,
655
(
1999
).
11.
H. N.
Bertram
,
Z.
Jin
, and
V. L.
Safonov
,
IEEE Trans. Magn.
38
,
38
(
2002
).
12.
J. C.
Mallinson
,
IEEE Trans. Magn.
38
,
3540
(
2002
).
You do not currently have access to this content.