Number sensitive detection and direct imaging of dipolar coupled magnetic nanoparticles by tunnel magnetoresistive sensors

Albon, C.; Weddemann, A.; Auge, A.; Meißner, D.; Rott, K.; Jutzi, P.; Hütten, A.
October 2009
Applied Physics Letters;10/19/2009, Vol. 95 Issue 16, p163106
Academic Journal
The suitability of magnetic tunnel junctions for the detection of magnetic nanoparticles is related to their scalability onto the nanoscale size regime without a significant loss of sensitivity. Elliptically shaped MgO based tunnel magnetoresistance sensors are used to provide a sharp detection of 14 nm Co nanoparticles. The measured signal is related to the degree of coverage of the sensor area by a nanoparticle layer. Moreover, the nanoparticles magnetostatic interaction on the sensor surface is clearly distinguished by the presence of a coercitive field in the detected signal. Experimentally obtained results are compared to theoretical models.


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