Scientists from the Laboratory for Epitaxial Nanostructures on Silicon and for Spintronics (LNESS) based in Como, Italy, in collaboration with P. Vavassori from the NanoGune Center in San Sebastian, Spain, have proposed a new sensing method that exploits the controlled displacement of magnetic domain walls (DWs) in ferromagnetic nanostructures.

The team has shown that DW can attract magnetic particles in solution. The particles in proximity of the active area of the device affect the displacement of the DW itself when an external field is applied. By measuring the anisotropic magnetoresistance signal during the displacement of the DW, the researchers have demonstrated the detection of a single particle measuring less than 100nm.

Particle capture and detection
The particles used are synthethic antiferromagnetic nanoparticles (SAFs) developed by Prof. Wang's group at Stanford University, US. The device, fabricated at the Univerisity of Illinois/Cornell Nanofabrication Facility, has been designed as a corner terminated with two disks to give one attracting magnetic pole represented by a mobile DW. In this way, the particles in solution are attracted to the sensing area DW, and then detected via an electrical readout when the DW is displaced.

The researchers presented their results in Nanotechnology.

About the author
Marco Donolato is a PhD student in the group of Prof. R Bertacco at LNESS, Italy. He is working on the detection and transport of magnetic particles using magnetic nanostructures in close collaboration with the Magnetic System group of Prof. M. F. Hansen at DTU-Nanotech, Denmark. This work has been financed by Fondazione Cariplo via the project "SpinBioMed".