MULTILEVEL AND THREEDIMENSIONAL NANOMAGNETIC RECORDING - Bio-Inspired and Nanoscale Integrated Computing - page 181

Today, perpendicular
recording is forcing
longitudinal recording
out of the market

Background:

Magnetizing
coil

MR reader

Perpendicular

Inductive
“ring” writer

Inductive
“SPH” writer

MR reader

Magnetizing
coil

S N N S S N N S S N N S

Write
field

Write field Recording media

Recording
layer

Longitudinal

Bit sizes: 13 x 52 nm 2

SUL

Figure 6.4. A schematic diagram to compare conventional longitudinal magnetic
recording and perpendicular magnetic recording systems. In these two cases,
magnetization in the recording media are directed along the plane and perpendi-
cular to the plane of the disk, respectively. (Image from Perpendicular Magnetic
Recording by S. Khizroev and D. Litvinov r 2004 Kluwer Academic Publishers.)

magnetic recording) and perpendicular recording. In the case of perpendicular
recording, the magnetization in the disk is polarized perpendicular to the disk.
This is in contrast to the conventional system in which the magnetization is
polarized along the disk. According to a model in layman's terms, each bit of
information is presented as a permanent magnet. Depending on the direction of
the magnetic moment inside the magnet, the recorded information is ''0'' or ''1.''
According to this model, one could pack more permanent magnets per unit
surface area in the configuration when the magnet's axis is directed perpendicular
to the disk rather than in the plane of the disk.
Unlike many other alternatives to the conventional recording (such as heat-
assisted magnetic recording (HAMR) and patterned media), perpendicular
recording has been quickly adopted by the industry because of its similarity to
the conventional technology [33-36]. In fact, this adoption is happening today.
During the last two years, most leading companies in the industry have transi-
tioned to perpendicular recording. Such a drastic change is quite unprecedented
for the industry that has been following one technology for over five decades now!
However, as mentioned earlier, perpendicular recording in its current form is
only a temporary solution/patch. The solution it offers is more quantitative than
qualitative and thus the expected progress is quite incremental (for only the next
five years or so).