The common method of magnetic disk recording in which vertical bits take up less space than horizontal bits. Also called "vertical recording," Toshiba and Seagate introduced perpendicular recording drives in the 2005-2006 time frame. Other vendors followed, and densities reached 400 gigabits per square inch by 2009. See areal density
A Trillion Bits Per Square Inch
Heat-assisted magnetic recording (HAMR) combines perpendicular recording with a laser to heat the medium and bumps areal density to more than a trillion bits per square inch (see HAMR
). See superparamagnetic limit
Perpendicular (Vertical) Recording
The magnetic flux coming out of the write pole (P2) affects the vertical bit directly below. It goes down to the soft underlayer and back up the return pole (P1).
Longitudinal (Horizontal) Recording
Before the perpendicular method, the bits were written horizontally on the disk platter. (Assistance with these illustrations courtesy of Hitachi Global Storage Technologies.)