Perpendicular recording
Perpendicular Recording or Perpendicular Magnetic Recording (PMR) (German: vertical recording or vertical recording ), also known as conventional magnetic recording (CMR) (German about: conventional recording method ), is a writing method for magnetic data carriers . The effect was demonstrated in 1976 by Shun-ichi Iwasaki at Tōhoku University in Japan and used commercially for the first time in 2005. PMR has been the current state of hard disk technology since 2010 at the latest.
functionality
In perpendicular recording, the magnetic moments , which together with the logical writing methods used, such as PRML, each represent a logical bit , are not parallel to the surface of the data carrier (longitudinal), but perpendicular to it (perpendicular). To put it loosely, the data go in-depth, so to speak. This leads to a potentially much higher data density (about three times as dense) than with the previous technology longitudinal recording ; This means that more data can be accommodated with the same surface.
The previously used longitudinal recording enabled a maximum data density of 15 to 30 gigabits per square centimeter. The stability of magnetic recordings is limited by the superparamagnetic effect , which means that bits of small size change their magnetization spontaneously (data loss). The volume representing one bit has a minimum size. She is u. a. depends on the coercive field strength and the temperature. Perpendicular recording allows a higher field strength in the volume to be magnetized, since the field lines emerge bundled from the tip and only have to overcome an air gap. A soft magnetic return is located behind the storage layer. It therefore enables a data density of up to 150 gigabits per square centimeter (1 terabit per square inch).
The disadvantage is that the smaller magnetic bits also require a shorter distance between the read / write head and the magnetic surface in order to be able to write and read the data. This recording technique is therefore technically more difficult to implement. The hard disk capacities can be increased by a maximum of ten times with this new recording technology. In addition, the significantly higher data density increases the read-write speed, as the read head reads more data per revolution and the data rate increases with the same number of revolutions. The method is now also used in a modified form in magnetic displacement and angle measuring systems to improve the measuring accuracy.
history
In August 2005 Toshiba was the first hard disk manufacturer to deliver a hard disk for end users with this technology. This first published type is a 1.8 "hard drive with a storage capacity of 40 GB and a rotation speed of 4200 revolutions per minute.
In April 2006, had Seagate announced the series Barracuda 7200.10 (750 GB) and Cheetah 15K.5 (server disks with 15,000 min -1 and max. 300 GB), the new TMR use -heads that a stronger read signal than conventional GMR -heads deliver.
See also
Individual evidence
- ↑ IBM shows perpendicular recording tape with 35 terabytes. Retrieved on November 14, 2013 : "... the perpendicular bit arrangement (Perpendicular Magnetic Recording, PMR) that is common today on hard drives ..."
- ↑ [1]
- ↑ Website from Highresolution with an explanation of the measuring process
- ↑ Seagate News and Factsheet ( PDF ; 138 kB) for the Cheetah 15K.5