Using magnetic permeability bits to store information

John Timmerwilke, J. R. Petrie, K. A. Wieland, Raymond Mencia, Sy Hwang Liou, C. D. Cress, G. A. Newburgh, A. S. Edelstein

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Steps are described in the development of a new magnetic memory technology, based on states with different magnetic permeability, with the capability to reliably store large amounts of information in a high-density form for decades. The advantages of using the permeability to store information include an insensitivity to accidental exposure to magnetic fields or temperature changes, both of which are known to corrupt memory approaches that rely on remanent magnetization. The high permeability media investigated consists of either films of Metglas 2826 MB (Fe40Ni38Mo4B18) or bilayers of permalloy (Ni78Fe22)/Cu. Regions of films of the high permeability media were converted thermally to low permeability regions by laser or ohmic heating. The permeability of the bits was read by detecting changes of an external 32 Oe probe field using a magnetic tunnel junction 10 μm away from the media. Metglas bits were written with 100 μs laser pulses and arrays of 300 nm diameter bits were read. The high and low permeability bits written using bilayers of permalloy/Cu are not affected by 10 Mrad(Si) of gamma radiation from a 60Co source. An economical route for writing and reading bits as small at 20 nm using a variation of heat assisted magnetic recording is discussed.

Original languageEnglish (US)
Article number405002
JournalJournal of Physics D: Applied Physics
Issue number40
StatePublished - Sep 10 2015


  • change
  • memory
  • permeability
  • phase

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films


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