"When exposed to a magnetic field, however, the resulting change in magnetic orientation of the electrodes affects electrons' ability to travel through the nanocontact," he said. "Depending on the size and material of the nanocontact and magnetization of the electrodes, the electrons will flow through either more or less easily."

This change can be measured by simple tools such as a voltmeter. On the bulk scale, magnetoresistance - the change in electrical resistance of a conductor when a magnetic field is applied - is only one factor in determining how easily electrons travel between electrodes. On the nanoscale, in which these magnetic field sensors will be constructed, magnetoresistance is the only cause of fluctuation in the flow of electrons.


The heart of Brankovic's system will consist of two magnetic electrodes, connected by a very small magnetic nanocontact. When exposed to a magnetic field, the flow of electrons through the nanocontact will change, yielding a measurable result.

Exactly how magnetoresistance works on this scale is unknown and will be one of the subjects of Brankovic's research. Two of the main theories to explain the phenomenon - both of which are supported by limited physical evidence - are incompatible. Brankovic has developed his own hypothesis that, if correct, would account for both sets of evidence.

"In my hypothesis, the nanocontact connecting the two electrodes is composed of non-conductive metal oxide that has metal channels that act as conductive pathways for electrons," Brankovic said. "When exposed to a magnetic field, some, but not all, of the channels of conductive material are altered either by the magnetic domain wall or by magnetostriction - the phenomena of a material's shape changing slightly when exposed to a magnetic field. Either of these explanations would result in a small but measurable change in the flow of electrons."

Whether this supposition proves correct or magnetic resistance on the nanoscale works in some other manner, Brankovic's goal will remain the same: to build a first-of-its kind magnetic field sensor that is far more powerful than any other sensor to date. If he succeeds, his invention will create a fundamental change in the arena of magnetic field detection.

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