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Proceedings Paper

Imaging magnetic noise sources in magnetic recording heads
Author(s): Lu Yuan; Jian-Xiang Shen; Bharat B. Pant; Sy-Hwang Liou
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Paper Abstract

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.

Paper Details

Date Published: 23 May 2005
PDF: 10 pages
Proc. SPIE 5843, Fluctuations and Noise in Materials II, (23 May 2005); doi: 10.1117/12.609457
Show Author Affiliations
Lu Yuan, Univ. of Nebraska/Lincoln (United States)
Jian-Xiang Shen, Seagate Recording Heads (United States)
Bharat B. Pant, Seagate Recording Heads (United States)
Sy-Hwang Liou, Univ. of Nebraska/Lincoln (United States)

Published in SPIE Proceedings Vol. 5843:
Fluctuations and Noise in Materials II
Peter Svedlindh; Dragana Popovic; Michael B. Weissman, Editor(s)

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