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Publication Citation: Soft magnetic layers for low-field-detection magnetic sensors

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Author(s): William F. Egelhoff Jr.; Robert D. McMichael; Cindi L. Dennis; Mark D. Stiles; Freemon Johnson; Alexander J. Shapiro; Brian B. Maranville; Cedric J. Powell;
Title: Soft magnetic layers for low-field-detection magnetic sensors
Published: May 18, 2006
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
Pages: pp. 90 - 92
Keywords: magnetic sensors pinning;synthetic antiferro-magnet
Research Areas: Nanomagnetics