Short for giant magnetoresistive, a hard disk drive storage technology. The term is usually referred to in reference to GMR heads. GMR heads are not named “giant” because of their size. The technology is named for the giant magnetoresistive effect, first discovered by two European researchers — Peter Gruenberg and Albert Fert — in the late 1980s. While working with large magnetic fields and thin layers of magnetic materials, Gruenberg and Fert noticed very large resistance changes when these materials were subjected to magnetic fields.

Disk drives that are based on GMR head technology use these properties to help control a sensor that responds to very small rotations on the disk. The magnetic rotation yields a very large change in sensor resistance, which in turn provides a signal that can be picked up by the electric circuits in the drive.

GMR heads are made up of four layers of thin material that combine into a single structure:

Free layer – The sensing layer. The free layer is passed over the surface of the data bits to be read. It is free to rotate in response to the magnetic patterns on the disk.
Spacer – Typically made from copper, this is a nonmagnetic layer that separates the magnetization of the free and pinned layers.
Pinned layer – A layer of cobalt material that is held in a fixed magnetic orientation by its proximity to the exchange layer.
Exchange layer – A layer of antiferromagnetic material that fixes the pinned layer’s magnetic orientation.

When the head passes over a magnetic field of one polarity, the electrons on the free layer turn to align with those on the pinned layer, creating a lower resistance in the head structure. When the head passes over a field of opposite polarity, the free layer electrons rotate so that they are not aligned with the electrons on the pinned layer. This causes an increase in the structure’s resistance. Because the resistance changes are caused by changes to the spin characteristics of electrons in the free layer, GMR heads are also known as spin valves, a term coined by IBM.

Read Also:


    Acronym for GNU Network Object Model Environment. (Pronounced guh-nome.) GNOME is part of the GNU project and part of the free software, or open source, movement. GNOME is a Windows-like desktop system that works on UNIX and UNIX-like systems and is not dependent on any one window manager. The current version runs on Linux, FreeBSD, […]

  • GNU

    Self-referentially, short for GNU’s not UNIX, a UNIX-compatible software system developed by the Free Software Foundation (FSF). The philosophy behind GNU is to produce software that is non-proprietary. Anyone can download, modify and redistribute GNU software. The only restriction is that they cannot limit further redistribution. The GNU project was started in 1983 by Richard […]

  • GOES

    Short for Geostationary Operational Environmental Satellites GOES is a series of geosynchronous satellites, first launched in the 1970’s by the United States and other governing bodies. GOES satellites are used to monitor storm development, such as tornadoes, hail storms or hurricanes and track the storm’s movements.

  • GOP

    In video terminology, when encoding in MPEG video GOP is the abbreviation for Group Of Pictures. In a motion sequence, GOPs are individual frames of pictures that are grouped together and played back so that the viewer registers the video’s spatial motion. The GOP allows editing and splicing of video material from different sources to […]

  • GPF

    Short for General Protection Fault, a computer condition that causes a Windows application to crash. The most common cause of a GPF is two applications trying to use the same block of memory, or more specifically, one application trying to use memory assigned to another application. The following situations can also cause GPFs. Running an […]

Disclaimer: GMR definition / meaning should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. All content on this website is for informational purposes only.