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What is Magnetoresistance?

Keith Koons
Keith Koons

The property of magnetoresistance is the ability to alter the path of electrical currents that are passing through an object by introducing an external magnetic field. The level of anisotropic magnetoresistance (AMR), or the rate at which particles are curved in another direction due to the presence of magnets, varies by the relative conductivity of the material being tested. This application allows electricity to pass over a larger surface area of an object to increase its overall resistance at the molecular level. By using different elements as variables, a formula can be applied to calculate the true magentoresistive effect, which allows many industries to determine which types of materials would be best-suited within their products.

As many breakthroughs have been made within this field of science since its discovery in 1856 by Irish inventor Lord Kelvin, this principle is now often referred to as ordinary magentoresistance (OMR). Colossal magnetoresistance (CMR) was the next classification to be adapted, and it is used to describe metals such as perovskite oxide’s ability to alter the resistance to much greater levels than previously thought possible. It was not until the latter parts of the 20th century that this technology was expanded upon even further.

Computer hard drives commonly used magnetoresistance technology.
Computer hard drives commonly used magnetoresistance technology.

In 1988, both Albert Fert and Peter Grünberg independently discovered the implementation of giant magnetoresistance (GMR), which comprises of stacking paper-thin metal layers of ferromagnetic and non-magnetic elements to either increase or decrease the overall resistance within the objects. Tunneling magnetoresistance (TMR) takes this concept one step further by causing the electrons to spiral perpendicularly, with the ability to transcend across the non-magnetic insulator. The insulator is usually comprised of crystalline magnesium oxide, which until recently, was thought to violate the natural laws of classical physics. This quantum mechanical phenomenon allows for several industries to implement TMR technologies that would otherwise be impossible.

Perhaps the most common example of magnetoresistance is the implementation of hard drives within computer systems. This technology enables the device to both read and write data in large volumes since the integrated microscopic heater coils allow superior control while the hard drive is in operation. This results in larger overall storage capacities with less frequent data loss. It is also used to empower the first generation of non-voliatle memory, which retains data even when a power source is not present.

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    • Computer hard drives commonly used magnetoresistance technology.
      By: Tomasz Zajda
      Computer hard drives commonly used magnetoresistance technology.