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Copper permalloys for fluxgate magnetometer sensors
Journal article   Open access   Peer reviewed

Copper permalloys for fluxgate magnetometer sensors

B Barry Narod and David M Miles
Geoscientific instrumentation, methods and data systems, Vol.13(1), pp.131-161
06/05/2024
DOI: 10.5194/gi-13-131-2024
url
https://doi.org/10.5194/gi-13-131-2024View
Published (Version of record) Open Access

Abstract

Fluxgate magnetometers are commonly used to provide high-fidelity vector magnetic field measurements. The magnetic noise of the measurement is typically dominated by that intrinsic to a ferromagnetic core used to modulate (gate) the local field as part of the fluxgate sensing mechanism. A polycrystalline molybdenum–nickel–iron alloy (6.0–81.3 Mo permalloy) has been used in fluxgates since the 1970s for its low magnetic noise. Guided by previous investigations of high-permeability copper–nickel–iron alloys, we investigate alternative materials for fluxgate sensing by examining the magnetic properties and fluxgate performance of that permalloy regime in the range 28 %–45 % Cu by weight. Optimizing the alloy constituents within this regime enables us to create fluxgate cores with both lower noise and lower power consumption than equivalent cores based on the traditional molybdenum alloy. Racetrack geometry cores using six layers of ∼30 mm long foil washers consistently yield magnetic noise around 4–5 pT/Hz at 1 Hz and 6–7 pT/Hz at 0.1 Hz, meeting the 2012 1 s INTERMAGNET standard of less than 10 pT/Hz noise at 0.1 Hz.
 Iron Noise Alloys Anisotropy Copper Cores Ferromagnetism Ferrous alloys Fluxgate magnetometers Investigations Iron constituents Laboratories Magnetic alloys Magnetic field Magnetic fields Magnetic properties Magnetometers Metallurgical constituents Molybdenum Molybdenum base alloys Nickel Noise measurement Patents Permeability Power consumption Sensors

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