A Christmas-Tree-Like Magnetic Field Sensor Based on Domain Wall Depinning in a Notched Nanowire

We propose a magnetic sensor with relatively high resolution that is based on domain wall (DW) pinning and depinning. In a nanowire patterned into a Christmas-tree-like geometry, asymmetric artificial notches serve as “bayonet locks”, which can pin a DW in one direction but allow it to pass in the other direction. The depinning field is linearly dependent on the inverse of the size of bayonet locks, and this dependence can be used to measure an external magnetic field. This concept is demonstrated with micromagnetic simulation, and the accuracy is experimentally estimated. At distances of nanometers, this type of sensor can be used to measure the magnetic fields of objects in biomedicine, such as cells labeled with immune-magnetic-nanoparticles.