About Joyce’s research on Integrated Magnetic Inductors/Transformers:

This research is aimed toward the application of magnetic films to integrated inductors and transformers.  The functionality of current devices is limited due to large device area on chip as well as low quality factors.  By adding a magnetic layer to structures, the inductance per mm can be increased.  Because the DC resistance is comparable to the air-core structure, the quality factor (ratio of magnetically stored energy to average dissipated power) can be enhanced within a limited frequency range.  At higher frequencies, the losses of the magnetic film and eddy currents will begin to grow, increasing the resistance at degrading the quality factor.

For the integrated inductor, a solenoid structure was chosen for its magnetic efficiency, as well its utilization of the full magnetic structure.  Because of the formation of a domain structure in the magnetic film, the high permeability that enhances the inductance becomes anisotropic, which does not lend itself to bends in the magnetic flux.

Experiments with geometry are carried out using Ansoft’s HFSS and Maxwell simulation software.  The magnetic films are sputter-deposited in the lab, and then analyzed using a permeameter, M-H loop tracer, and a Kerr-Effect microscope, which can be used to view the domain structure of the films.