Database Reference
In-Depth Information
Recording head
Longitudinal recording
Media
Track width
S
N
N
SS
N N
SS
N
Bit length
(a)
N
S
N
S
N
S
N
S
N
S
(b)
Figure 1.2
Longitudinal recording devices (a) currently dominate the mar-
ket. However, the superparamagnetic effect limits areal densities of this tech-
nique to 150 Gbits/mm
2
. Perpendicular recording (b) promises to support
continued scaling of areal density up to 1 Tbit/mm
2
because neighboring
domains complement rather than counteract each other's polarity. This im-
proves the stability of the recording and thereby overcomes the challenges of
superparamagnetism.
perpendicular to the storage medium where the demagnetizing fields tend
to have less interaction between neighboring bits. Perpendicular recording is
expected to support continued improvements to storage densities that top out
at about 1 terabit/mm
2
. The first commercial products incorporating verti-
cal recording technology were introduced in 2005 with bit densities of 170
gigabits/mm
2
, with density doubling approximately every two years.
1.2.6 Future Trends
Figure 1.3 summarizes trends in storage density and cost per bit. The cost
trends depicted in Figure 1.3(b) are strongly dependent on the ability to
improve bit densities in Figure 1.3(a) at exponential rates. When a storage
