Magnetoresistance

Magnetoresistance

Subject: science and technology

Context: Recently, researchers in the UK, led by Nobel laureate Andre Geim have found that graphene displays an anomalous giant magnetoresistance (GMR) at room temperature.

Magnetoresistance:

• GMR is the result of the electrical resistance of a conductor being affected by magnetic fields in adjacent materials.
• Say a conductor is sandwiched between two ferromagnetic materials (commonly, metals attracted to magnets, like iron). When the materials are magnetised in the same direction, the electrical resistance in the conductor is low. When the directions are opposite each other, the resistance increases. This is GMR.
• GMR-based devices are particularly used to sense magnetic fields.
• It is used in harddisk drives and magnetoresistive RAM in computers, biosensors, automotive sensors, microelectromechanical systems, and medical imagers.
• The 2007 Nobel Prize in Physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR

Findings of the Study:

• In their study, the magnetoresistance in monolayer graphene at 27º C held between two layers of boron nitride increased by 110% under a field of 0.1 tesla. To compare, the magnetoresistance in these conditions increases by less than 1% in normal metals.
• The magnetoresistance observed in the graphene-based device was almost 100-times higher than that observed in other known semimetals in this magnetic field range
• The new study has found that a graphene-based device, unlike conventional counterparts, wouldn’t need to be cooled to a very low temperature to sense these fields.

More about Graphene: https://optimizeias.com/graphene/