Characterization of single magnetic particles with InAs quantum-well Hall devices

We have measured the magnetic dipolar field from individual micron-sized spherical ferromagnetic particles. The particles were positioned using an atomic force microscope and measured using submicron Hall sensors fabricated from an InAs single-quantum-well heterostructure with lateral dimensions of 0.5–2.5μm. The magnetic moment of individual particles has been measured, verifying their dipolar moment. We also demonstrate a scaling rule for the detection of individual particles which is relevant to the design of biosensors.