Datasheet

PERPENDICULAR RECORDING—AN OLD THEORY BECOMES REALITY

One solution to the problem of self-erasure has been to align the particles vertically in the

coating rather than end to end so that more magnetic domains can be packed in the

coating. Poles of opposite polarity attract each other, so positive poles next to negative

poles can reinforce each other. Since the morphology (shape) of the domain is

perpendicular rather than horizontal, there is less self-erasure and sharper delineation of

the flux patterns that can be recorded on the vertical tips of the magnetic particles than on

their ends. See Figure 4.

This new arrangement of magnetic domains allows “perpendicular recording,” a goal of

magnetic media manufacturers for some time because of the dramatic increase in flux

density allowed by magnetic domains standing head to toe instead of lying end to end.

Hard drive manufacturers are just now moving to perpendicular recording as a means to

increase storage capacity without increasing the size of the drives or media. Optical

recording will only see such a dramatic leap in density when it moves to holographic

recording instead of using single wavelengths of light in molded pits.

Greater Flux Density of

Perpendicular Recording

End to end distribution of single magnetic domains

Greater flux density with perpendicular alignment

Less self-erasure of magnetic domains

Figure 4

MAGNETIC RECORDING VERSUS SOLID STATE

There are factors other than recording density that determine which medium is best suited

for storage. Two of the most significant factors are cost and reliability. Cost is generally

calculated as the cost per gigabyte of capacity. Magnetic media, including tape products,

generally have held a significant advantage simply because the storage density of such

media is so large per unit. Despite their complexity, micro hard drives maintain that

advantage over less complex devices such flash media. The costs of flash media

continue to decrease as memory chips become less expensive and production

Critics of optical recording can liken today’s methods of using light patterns bounced off molded

pits as a “more advanced method of IBM’s old punch-card technology.”