Design and optimisation of a novel magnetic detection scheme for encoded magnetic information carriers.

Abstract

Previous work in the field has outlined a method to create micron-sized, tuneable encoded magnetic information carriers that can be redeposited through a liquid suspension. This thesis aims to build on this work, further characterising the information carriers and presenting a possible novel detection technique. The magnetic information carriers in this work use synthetic antiferromagnetic (SAF) particles with perpendicular magnetic anisotropy (PMA), attenuating the coupling strength between the magnetic layers using a platinum interlayer. This provides a controllable magnetic parameter which is used as the basis for the magnetic encoding. These particles can be lifted off the substrate into a solution for redeposition onto a surface which provides a magnetic ‘tag’. The particles are presented and characterised, including statistical distributions of switching events to better understand their detectable properties. A novel detection scheme for these particles is then proposed using inductive sensing and a rotating permanent magnet as a drive field source. Device efficacy is evaluated using computational simulations, allowing for the optimisation of the parameter space before physical building. The efficacy of different input parameters is evaluated using a figure of merit – the number of possible channels the detector can measure. The simulations begin with an idealised model of the detector and particle set, with zero coercivity SAF particles and perfect alignment. The different methods that the detector can be used in are assessed, as well as exploring the possible input geometries. Real-world constraints are later built into the model including the switching distributions of particles and the effects of misalignment. From these, the build constraints and electronic requirements of the system can be characterised. The detector is finally presented virtually through computer-aided design, which would be used to create a prototype model of the device.