Office of Technology Transfer – University of Michigan

Epitaxial Magnetic Sensors

Technology #1735

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Roy Clarke
Managed By
Joohee Kim
Licensing Specialist, Physical Sciences & Engineering 734-764-8202


Magnetic storage technology has increasing growth rate, which has enabled the hard disk drive industry to drive costs down. While many factors such as fly height, media, etc. can also be improved, magnetic recording heads capable of higher speeds and densities are the key to continuing this trend. The magnetic sensing used so far, is done by a change in magnetoresistance (MR) induced in the sensing head. One promising source of large MR effects has been magnetic tunnel junctions (MTJs). Although MTJ structures have been studied for more than twenty years, it is only recently that significant changes in MR have been observed.


Researchers at the University of Michigan have invented a magnetic tunneling structure with improved MR effect in comparison to conventional magnetic tunneling structures. The structure consists of ferromagnetic layers and an insulating tunneling barrier layer sandwiched in between. The two ferromagnetic layers are single crystalline and polycrystallilne which work in combination to provide two states of magnetization, and the insulating layer is preferably a nitride layer. This structure provides lower absolute electrical impedance, higher degree of polarization of the ferromagnetic layers, lower tunneling barrier, as well as reduced in size. The structure also has an oxide-free tunneling barrier and reduced oxidation between the ferromagnetic layers and the insulating tunneling barrier layer.

Applications and Advantages


  • Magnetic tunneling structure for magnetic storage devices


  • Lower absolute electrical impedance and tunneling barrier
  • Reduced size
  • Oxide-free tunneling barrier and reduced oxidation between ferromagnetic and insulating tunneling barrier layers