Chapter 5
247
Measurement Definition
Measurement Parameter Definition
1.
Ch
apt
er
T
itl
e
2
. Cha
p
te
r T
itle
3
. Chap
te
r T
itle
4
. Chap
te
r T
itl
e
M
e
as
ur
em
e
n
t
De
finit
ion
1. Erase the track as specified by the “hpe5022_erase” function.
2. Write HF (high frequency) data pattern given by the function “hpe5022_hfPattern”.
3. Measure the HF-TAA.
4. Erase the track as specified by the “hpe5022_erase” function.
5. Write LF (low frequency) data pattern given by the function “hpe5022_lfPattern”.
6. Measure the LF-TAA.
7. Iterate steps 1 to 6 to get the average of measurement results.
Time Asymmetry Measurement
Time asymmetry is used to determine the pinned layer reversal of the GMR head. Time
asymmetry is defined as 1/4 the difference between the adjacent pulse pair spacings, T
l
and
T
s
, averaged over many pulse pair spacings. This method is considered as traditional, since
it requires more complex measurement equipment and longer measurement time. In time
asymmetry, if the transition time from positive pulse to negative pulse is less than the
transition time from negative pulse to positive pulse, the head is said to be normal. If it’s
the opposite then the head is considered damaged.
Time asymmetry can be measured by waveform measurement (using an oscilloscope.)
Figure 5-7
T
l
and T
s
Definition
Equation 5-7
Time Asymmetry Definition
•
Tl denotes the time distance from positive peak transition to negative peak transition
(p-n).
TimeAsymmetry
1
N
----
T
l
T
s
Ð
4
-----------------
i
1
=
N
∑
=
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