Perpendicular recording

Perpendicular recording (or Perpendicular Magnetic Recording, PMR) is a technology for data recording on hard disks. It was first proven advantageous in 1976 by Shun-ichi Iwasaki, then professor of the Tohoku University in Japan, and first commercially implemented in 2005.

Advantages

Perpendicular recording can deliver more than three times the storage density of traditional longitudinal recording. There was some interest in using the system in floppy disks in the 1980s, but the technology was never reliable. Since about 2005 the technology has come into use for hard disk drives. Hard disk technology with longitudinal recording has an estimated limit of 100 to 200 gigabit per square inch due to the superparamagnetic effect, though this estimate is constantly changing. Perpendicular recording is predicted to allow information densities of up to around 1 Tbit/sq. inch (1000 Gbit/sq. inch)..

Technology

The main challenge in designing magnetic information storage media is to retain the magnetization of the medium despite thermal fluctuations caused by the superparamagnetic limit. If the thermal energy is too high, there may be enough energy to reverse the magnetization in a region of the...
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