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FE Malaysia Products

Hard Disk Drive
3.5inch vs 2.5inch
Longitudinal Magnetic
  Recording (LMR)
Perpendicular Magnetic
  Recording (PMR)
Insulated Gate Bipolar
  Transistor (IGBT)

Longitudinal Magnetic Recording (LMR)

The type of media products which are made prior to 2006 is termed as Longitudinal Magnetic Recording (LMR) Media. LMR media means that the data, or magnet, has a magnetic direction facing within the in-plane direction of the disk, just like the image above. This is the same way data has been stored in video cassettes, tapes, and floppy disks over the last 20~30 years.

However, LMR media has limits to how small the magnet (bit) can be. And this is called as the super-paramagnetic effect, where the magnet becomes unstable when it reaches a certain amount of volume. The magnet will be highly susceptible to outer magnetic fields from other sources and will eventually change its orientation accidentally, thus causing HDD to having errors. To counter this, LMR has to have larger grain size, however, if the volume of the magnet is too large, it will also be susceptible to noise, which will in turn weaken the signal which is supposed to be read by the head.

The media industry has developed a thin layer design to counter this effect, which is called as Anti-Ferromagnetic Coupling (AFC). This works by inserting a thin insulator between two layers of magnets, thus increasing the stability of the magnet by coupling both layers.


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