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A device named magnetic susceptometer for a complete determination of the magnetic complex susceptibility of materials and minerals has been conceived and manufactured as a complement for the in situ characterization of rocks during high resolution magnetic prospections. In this work a device and its capabilities for susceptibility measurements are described, the calibration performed with artificial samples, and the values of real and imaginary susceptibility of natural samples in a range comprising: χ = 10−4 to 10−7 [SI], representative of Earth and also Mars rocks.

In this paper we describe the development of devices devoted to the characterization of the magnetic complex susceptibility of materials and minerals. The work is focused on the evolution, calibration and validation of the prototypes foreseen in H2020 NEWTON project, a magnetic susceptometer for the in-situ characterization of rocks during high resolution magnetic prospections, with characteristics compatible with space vehicles and hand-held instrumentation. The instrument consists of a novel susceptometer design based on an inductive method and a COTS magnetometer for the vector magnetic field characterization. The calibration and validation process for Prototype 1 casted very good results in comparison with other commercial and high resolution laboratory devices, reaching a resolution in the order of χ = 10 - 4 (I.S. Vol. Susceptibility), representative of Earth, Moon and Mars rocks. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 730041. Peerreview

Anisotropic magnetoresistive (AMR) magnetic sensors are often chosen as the magnetic transducer for magnetic field sensing in applications with low to moderate magnetic field resolution because of the relative low mass of the sensor and their ease of use. They measure magnetic fields in the order of the Earth magnetic field (with typical sensitivities of 1‰/G or 10−2‰/μT), have typical minimum detectable fields in order of nT and even 0.1 nT but they are seriously limited by the thermal drifts due to the variation of the resistivity with temperature (∼2.5‰/°C) and the variation of the magnetoresistive effect with temperature (which affects both the sensitivity of the sensors: ∼2.7‰/°C, and the offset: ±0.5‰/°C). Therefore, for lower magnetic fields, fluxgate vector sensors are generally preferred. In the present work these limitations of AMR sensors are outlined and studied. Three methods based on lock-in amplifiers are proposed as low noise techniques. Their performance has been simulated, experimentally tested and comparatively discussed. The developed model has been also used to derive a technique for temperature compensation of AMR response. The final goal to implement these techniques in a space qualified applied specific integrated circuit (ASIC) for Mars in situ exploration with compact miniaturized magnetometers. Peerreview

In this paper we present an analytical model for describing the sensitivity of a toroidal fluxgate sensor. The model is based on a simplified schematics for the hysteresis loop of the fluxgate core that only includes the coercivity, the saturation field and the saturation magnetization. In spite of this simplicity, the model has been successfully used to describe the variation of the sensitivity of a PCB-based fluxgate sensor with the amplitude and the frequency of the driving current. The model has been developed for a toroidal configuration but can be easily modified to describe other geometries.

A device to obtain an estimate of the spectrum of a time‐variable magnetic field has been developed. The amplitude of each spectral component of the magnetic field series is obtained by analyzing with a double demodulation technique the signal generated from a flux‐gate‐like detector operating in open loop configuration. This device shows a sensitivity of about 1 mV/nT in the range from 0 to 300 Hz. For frequencies higher than 300 Hz the sensitivity decreases, and a correction factor that depends on the transfer function of the electronic device must be applied. The present device can be applied to environmental measurements, industrial applications, traffic control, and scientific research.

We report the design, fabrication, and characterization of a new system that combines the performances of two different types of magnetic characterization systems, Alternating Gradient Force Magnetometers (AGFM) and susceptometers. The flexibility of our system is demonstrated by its capability to be used as any of them, AGFM or susceptometer, without any modification in the experimental set-up because of the electronics we have developed. Our system has a limit of sensitivity lower than 5 × 10(-7) emu. Moreover, its main advantage is demonstrated by the possibility of measuring small quantities of materials under DC or AC magnetic fields that cannot properly be measured with a commercial vibrating sample magnetometers or AGFM.

CoP electrolytic monolayers and multilayers were grown over copper wires using a constant or pulsed electrical current density, exhibiting radial or planar anisotropy, respectively. Over the surface of a monolayer, multilayers of different thicknesses were deposited. The surface radial anisotropy evolves to a planar one as the overlayer thicknesses increase. The surface magnetization is coupled with the bulk anisotropy for overlayer thickness up to ≈ 2 μm.