What is "perpendicular recording"

n. A technique of creating magnetic data storage using vertical as opposed to longitudinal magnetization. Becoming more common now in laptop hard disk drives.

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. The first industry-standard demonstration showing unprecedented advantage of PMR over longitudinal magnetic recording (LMR) at nanoscale dimensions was made in 1998 at IBM Almaden Research Center in collaboration with researchers of Data Storage Systems Center (DSSC) – a National Science Foundation (NSF) Engineering Research Center (ERCs) at Carnegie Mellon University (CMU).