Magnetic Reversal

Research Interests

Magnetic quantum cellular automata (MQCA) are an alternative computing architecture from the current architecture. A possible implementation of MQCA is single domain ferromagnetic particles. These single domain particles are designed so they have two possible magnetization states. The dominant factor controlling the switching field distribution between these two states is unknown: imperfections, shape, anisotropy variations as well as interactions with neighbors can all influence this distribution. By gaining insights into the currently poorly understood magnetic reversal modes of these systems, we will be many steps closer to our far-term goal of determining if such arrays can be used as MQCA.

Ferromagnetic samples of Permalloy are made by sputtering 20 nm of material through a stencil on to an electron transparent silicon nitride membrane. The stencils are made by milling holes in a silicon nitride membrane using a focused ion beam (FIB) at ecole polytechnique de Montreal.

These particles will be measured using Magnetic force microscopy (MFM), structurally characterized by Transmission electron microscopy (TEM) and compared with simulations. An MFM with in-situ magnetic field is used to study the magnetic reversal of these particles as a function of temperature, angle and magnitude of the applied magnetic field. Detailed morphological and chemical characterization of individual particles will be performed by TEM to determine variability of structural and chemical composition. The measured variability will be correlated to differences in switching fields.


Home built Magnetic force Microscope

6um wide MFM image of Permalloy structures

Magneto Optical Kerr Microscope

Image of MOKE setup

FIB (Ecole Polytechnique de Montreal)

Image of stencil made with the FIB

TEM (McGill)


Group Members

  • Jeff Bates (PhD student)


  • Yoichi Miyahara (McGill University)
  • Dr. Jan Sandtner and Prof. Hannes Bleuler (Ecole Polytechnique Federale de Lausanne)