Imaging magnetic noise sources in magnetic recording heads

L. Yuan, J. X. Shen, Bharat B. Pant, S. H. Liou

Research output: Chapter in Book/Report/Conference proceedingConference contribution


A detailed understanding of noise characteristics is essential for the design of a high signal-to-noise ratio (SNR) reader sensor. We intend to correlate the microstructure to the source of magnetic noises for improving the magnetic stability of the recording heads. A dynamic magnetic sensitivity mapping (MSM) system is designed to image the magnetic noise sources in sub-micrometer sized recording heads. A nanometer sized magnetic force microscopy (MFM) tip was used to apply a well-defined, localized magnetic field on the air bearing surface (ABS) of the head. For a certain area position of the free layer with incoherent rotation of the magnetic moment, this localized magnetic field will cause magnetic instability in the head, and this instability will show up as electrical noise on the output signal. Because most of the noise related to magnetic domain fluctuation is dominated at the low frequency region, our study concentrates on the spatial characterization of the noise source in a frequency range of 20 kHz to 60 kHz. Recording the average amplitude of the noise spectrum due to the excitation in the measured frequency range as a function of the tip's position, the location of the magnetic noise source can be identified. Magnetic noise images have been obtained by our system for some recording giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) recording heads. Noise MSM images of some unstable recording heads clearly show the spatially uneven noise.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsP. Svedlindh, D. Popovic, M.B. Weissman
Number of pages10
StatePublished - 2005
EventFluctuations and Noise in Materials II - Austin, TX, United States
Duration: May 24 2005May 25 2005


OtherFluctuations and Noise in Materials II
Country/TerritoryUnited States
CityAustin, TX


  • Magnetic force microscopy
  • Magnetic noise
  • Magnetic recording heads

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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