Also known as conventional magnetic recording (CMR), is a technology for data recording on magnetic media, particularly hard disks.
It was first proven advantageous in 1976. First commercially implemented in 2005. The first industry-standard demonstration showing unprecedented advantage of PMR over longitudinal magnetic recording (LMR) at nanoscale dimensions was made in 1998.
In perpendicular recording, data bits are aligned vertically – or perpendicular to the disk, allowing room for more data. Perpendicular recording can deliver more than three times the storage density of traditional longitudinal recording.
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.
The main challenge in designing magnetic information storage media is to retain the magnetisation 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 magnetisation in a region of the medium, destroying the data stored there. The popular explanation for the advantage of perpendicular recording is that it achieves higher storage densities by aligning the poles of the magnetic elements, which represent bits, perpendicularly to the surface of the disk platter.
In the early 2000s, three important factors came together which allowed perpendicular recording to exceed the capabilities of longitudinal recording and led to commercial success. First, the development of media with an oxide-segregant exchange-break between grains. Second, the use of a thin ‘cap’ on the media to control the level of exchange-coupling between grains and to enhance propagation of switching through the thickness of the medium. Third, the introduction of the trailing-shield head invented by Michael Mallary. This head offered higher field gradients and more favourable field angles than a simple pole head.
Perpendicular recording technology however will not start and stop with changing the way data bits are aligned. Much like the growth in capacity with longitudinal recording, technological advancements in platters; read/write heads, and physical disk media surfaces to name a couple, will contribute to advancements in the capacity growth of perpendicular hard disk drives.