Low-noise permalloy ring cores for fluxgate magnetometers

Abstract

Abstract. Fluxgate magnetometers are important tools for geophysics and space physics, providing high-precision magnetic field measurements. Fluxgate magnetometer noise performance is typically limited by a ferromagnetic element that is periodically forced into magnetic saturation to modulate, or gate, the local magnetic field. The parameters that control the intrinsic magnetic noise of the ferromagnetic element remain poorly understood. Much of the basic research into producing low-noise fluxgate sensors was completed in the 1960s for military purposes and was never publicly released. Many modern fluxgates depend on legacy Infinetics S1000 ring cores that have been out of production since 1996 and for which there is no published manufacturing process. We present a manufacturing approach that can consistently produce fluxgate ring cores with a noise of ∼6–11 pT per square root hertz – comparable to many of the legacy Infinetics ring cores used worldwide today. As a result, we demonstrate that we have developed the capacity to produce the low-noise ring cores essential for high-quality, science-grade fluxgate instrumentation. This work has also revealed potential avenues for further improving performance, and further research into low-noise magnetic materials and fluxgate magnetometer sensors is underway.

Noise Suppression in Parallel Fluxgate Magnetometers by DC-Biased Excitation Method

“…Many parallel fluxgate magnetometers have been developed so far, as introduced in 1), 2), and 3). Recently, Miles et al 14) developed low-noise permalloy ring cores for parallel fluxgate magnetometers which achieved noise level of 6 to 11 pT/Hz 1/2 . There is a possibility to reduce the noise level of those sensors using the DC-biased excitation method.…”

MagneToRE: Mapping the 3-D Magnetic Structure of the Solar Wind Using a Large Constellation of Nanosatellites

“…In this scenario, which is summarized in Table 3, many of the spacecraft support systems would be based on components developed at the Space Sciences Laboratory at the University of California, Berkeley (UCB/SSL) for the Cubesat Radio Interferometry Experiment (CURIE) mission (Sundkvist et al, 2016), which is slated to launch and operate in late 2021. Likewise, the probe magnetometers would be based on instruments and technology (e.g., Miles et al, 2019) developed at the University of Iowa (UIowa).…”

“…This system, based on the MGF instrument (Wallis et al, 2015) on Cassiope/ e-POP, also draws heritage from the fluxgate magnetometer (Miles et al, 2016) for the Ex-Alta 1 CubeSat (Mann et al, 2020) in the QB50 constellation (Wicks and Miles, 2019). The next-generation, nanosatellite-scale "Tesseract" magnetometer sensor (Figure 7A) leverages low-noise custom fluxgate cores (Miles et al, 2019) to create a compact, rigid, symmetric, and magnetically stable probe. This sensor design also incorporates temperature compensation (Miles et al, 2017), which may be advantageous for some potential trajectories (e.g., lunar orbit; Section 4.2).…”

Ultrasensitive Magnetic Field Sensors for Biomedical Applications

“…Hz [62][63][64] and even down to 100 fT/ √ Hz with the device based on epitaxial yttrium iron garnet films having a specially graded edge profile [65]. The detection signal frequency is in the low-frequency range (from 1 Hz to 100 Hz) which is suitable for the measurement of magnetocardiography, magnetoencephalography, and magnetomyography signals.…”