Read Back Signals in Magnetic Recording - Research Group Fidler

Analytical Calculations
t
C
8
π
= . (3.15)
Inserting in (3.11) leads to the final result for the head field
⎛γ x( x + gz , ) −γx( xz , ) −γx( − x+ gz , ) +γx( −xz
, ) ⎞
MSL t ⎜ ⎟
H H ( xz , ) = ⋅ 0
8 g ⎜ ⎟
. (3.16)
⎜γ z( x + gz , ) −γ z( xz , ) +γz( − x+ gz , ) −γz( −xz
, ) ⎟
⎝ ⎠
Now a normalized head field H H can be introduced, which is independent from the sensor
magnetization
H
n
H
⎛γ x( x + gz , ) −γ x( xz , ) −γ x( − x+ gz , ) + γ x(
−xz
, ) ⎞
t ⎜ ⎟
( xz , ) = ⋅ 0
8 g ⎜ ⎟
. (3.17)
⎜
z( x + gz , ) − z( xz , ) + z( − x+ gz , ) − z(
−xz
, ) ⎟
⎝γ γ γ γ ⎠
Figure 3.3 shows the normalized head field at z = − 10 nm and for t = 5 nm and g = 27.5 nm ,
so that the total gap is 60 nm. For longitudinal recording only the x-component contributes,
because the magnetization points mainly in this direction.
H x
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-100 -50 0 50 100
x [nm]
H z
-0.02
-100 -50 0 50 100
x [nm]
Figure 3.3: The x- and the z-component of the normalized head field of a read head with
60 nm gap, and sensing layer thickness 5 nm, 10 nm below the ABS.
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
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