Soft magnetic layers for low-field-detection magnetic sensors

Published

May 18, 2006

Author(s)

William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Freemon Johnson, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell

Abstract

We have investigated a wide variety of soft magnetic layers as sense layers for magnetic-field sensors. We find that in thin-film form, some of these soft materials can have susceptibilities (?) approaching those of the corresponding bulk material. In general, the highest ? values occur in trilayer structures with a non-magnetic film separating two soft magnetic films. The alloy Ni77Fe14Cu5Mo4 of the mu-metal family is the softest thin-film material we have found, and we can achieve hard-axis ? values above 105 in trilayer structures. The hard axis is preferred for magnetic sensors due to its near-linear response. The major impediment we have found to using these very soft layers in low-field sensors is that the _X value decreases by almost two orders of magnitude when the soft structure is incorporated in a standard spin valve or tunnel junction. The problem appears to be stiffening of the soft layer by the stray field from ripple in the pinned layer. A partial solution is found in the use of a synthetic antiferromagnetic as the pinned film. The antiferromagnetic alignment appears to have a canceling effect on the stray field.

Citation

Thin Solid Films

Volume

505

Issue

1-2

Pub Type

Journals

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Keywords

magnetic sensors pinning, synthetic antiferro-magnet

Citation

Egelhoff Jr., W. , McMichael, R. , Dennis, C. , Stiles, M. , Johnson, F. , Shapiro, A. , Maranville, B. and Powell, C. (2006), Soft magnetic layers for low-field-detection magnetic sensors, Thin Solid Films, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=620582 (Accessed April 19, 2024)