Temperature cue to graphene sensitivity
doi:10.1038/nindia.2014.22 Published online 18 February 2014
Researchers have gained new insights into the magnetic properties of graphene oxide and reduced graphene oxide at room and low temperatures under the influence of a magnetic field1 . These insights will be very useful for fabricating graphene-based electronic devices.
Studies have shown that the magnetic properties of graphene stem from the presence of structural defects and oxygen-containing groups. However, no previous studies had investigated how the magnetic properties of graphene evolve with changing temperature.
To probe how the magnetic properties of graphene vary with temperature, the researchers synthesized sheets of graphene oxide. They then converted some of these sheets into reduced graphene oxide by using the reducing agent hydrazine hydrate. They analysed the magnetic properties of graphene oxide and reduced graphene oxide by exposing the samples to a specific magnetic field at various temperatures.
At ten degrees above absolute zero, both graphene oxide and reduced graphene oxide exhibited paramagnetism. Reduced graphene oxide was found to be less paramagnetic than graphene oxide at this low temperature. At room temperature, graphene oxide and reduced graphene oxide exhibited antiferromagnetic or ferromagnetic properties.
The researchers suggest that the samples are paramagnetic at low temperature due to the presence of defects and patches of hydroxyl groups. The patches of hydroxyl groups may act as nanosized single-domain particles, which contribute to paramagnetism by responding to an external magnetic field.
"Experimental evidence of magnetism at room temperature in graphene-based nanostructures will make them attractive materials for developing electronic devices that exploit the spin properties of electrons," says Sangam Banerjee, a senior author of the study.
The authors of this work are from: Saha Institute of Nuclear Physics, Surface Physics Division, Kolkata and Material Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India.
- Bagani, K. et al. Anomalous behaviour of magnetic coercivity in graphene oxide and reduced graphene oxide. J. Appl. Phys. 115, 023902 (2014)