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Partial Erasure Measurement
Partial Erasure is also referred to as 'nonlinear amplitude loss' that occurs at high recording
densities when two transitions (dibit) are written closely with a narrow separation,
resulting to amplitude loss of the read back signal when data is read.
As shown in Figure 5-54, isolated transition 1 is written with a typical zigzag structure and
is isolated from other transitions. Transitions 2 and 3 are closely written forming a dibit.
When transition 3 is being written, it produces a demagnetization field which is opposite to
the direction of the media's magnetization. This demagnetization field is largest at the
transitions tips and closest to the previously written data.
Since the separation between transitions 2 and 3 is too narrow. The zigzag tips of
transitions 2 and 3 will cause the demagnetization field to reverse the magnetization
between the tips resulting to a partial erasure of transitions 2 and 3, splitting it into isolated
granules of magnetization.
Figure 5-54
Partial Erasure
Equation of Partial Erasure is defined as:
Partial Erasure is executed by writing a 3T data pattern and by measuring its amplitude
(V3T) at the third harmonic frequency. Then, 1T data pattern is written and measure the
amplitude (V1T) at the same frequency.
Equation 5-28
Partial Erasure Definition
Partial Erasure does not cause bit shift errors since it is not influenced by 'non-linear
Chapter 5
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V
1
1T
----------------- -
PE
=
-- -
Ð
×
6
V
2
3T
Measurement Definition
Other Measurement Definitions
305
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