Single molecule detection with magnetic beads—computer simulation

The detection of single molecules, e.g. in biology is possible by marking the interesting molecules with magnetic beads and detect the influence of the beads on a GMR/TMR/SV multilayer. The development of suitable sensors has been studied experimentally as well as theoretically in order to optimize the sensor parameters. A FD method including the usually used contributions to the total energy (exchange, af coupling, anisotropy and magnetostatic) is used for the simulation with additional contributions to the local field according to the stray fields of the beads. In this work, we present the results of micromagnetic calculations of the magnetization behavior of GMR/TMR sensors considering also the dipole fields of the beads as additional contributions to the local field.