Researchers in the UK, led by Nobel laureate Andre Geim, have discovered magnetoresistance in graphene – a single-atom-thick layer of carbon atoms bonded in a honeycomb pattern – that further distinguishes this ‘wonder’ material.

Graphene’s anomalous Giant Magnetoresistance (GMR)

• Graphene displayed an anomalous giant magnetoresistance (GMR) at room temperature.
• GMR is the result of the electrical resistance of a conductor being affected by magnetic fields in adjacent materials.
• It is used in hard disk drives and magnetoresistive RAM in computers, biosensors, automotive sensors, micro-electromechanical systems, and medical imagers.

What is GMR?

• GMR is a phenomenon where the electrical resistance of a conductor is 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.

Significance of the finding

• 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.
• In the 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 team attributed this to the presence of a ‘neutral’ plasma and the electrons’ mobility.

Try this MCQ

Which of the following best describes magnetoresistance?

(a) The magnetic resistance of a conductor to electrical current flow

(b) The phenomenon where the electrical resistance of a conductor is affected by magnetic fields in adjacent materials

(c) The ability of a conductor to produce a magnetic field when an electrical current is passed through it

(d) The resistance of a magnet to demagnetization by an external magnetic field

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