Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

Lima, Eduardo A.; Weiss, B. P.

doi:10.1002/2016gc006487

Cited by 43 publications

(51 citation statements)

References 60 publications

(99 reference statements)

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“…The sample magnetic field is generated by field sources, such as current densities or magnetic dipoles, with either known or unknown distributions. Measurement of the sample magnetic field can be used for the inverse problem of estimating an unknown source distribution under certain conditions [40][41][42]. The form of the sample magnetic field in terms of its sources is…”

Section: Sample Fieldsmentioning

confidence: 99%

Principles and techniques of the quantum diamond microscope

et al. 2019

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We provide an overview of the experimental techniques, measurement modalities, and diverse applications of the Quantum Diamond Microscope (QDM). The QDM employs a dense layer of fluorescent nitrogen-vacancy (NV) color centers near the surface of a transparent diamond chip on which a sample of interest is placed. NV electronic spins are coherently probed with microwaves and optically initialized and read out to provide spatially resolved maps of local magnetic fields. NV fluorescence is measured simultaneously across the diamond surface, resulting in a wide-field, two-dimensional magnetic field image with adjustable spatial pixel size set by the parameters of the imaging system. NV measurement protocols are tailored for imaging of broadband and narrowband fields, from DC to GHz frequencies. Here we summarize the physical principles common to diverse implementations of the QDM and review example

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Section: Sample Fieldsmentioning

confidence: 99%

Principles and techniques of the quantum diamond microscope

et al. 2019

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“…Thus, previous studies had to sacrifice temporal resolution that speleothems could potentially offer. Whereas scanning SQUID microscopy (SSM) can image very weak magnetic fields above natural geologic sample with a high spatial resolution of ~ 100 µm (e.g., Lima and Weiss, 2016;Oda et al, 2016), which could likely solve the problem of weak magnetism associated with Speleothem based paleomagnetic studies. To date, only a few preliminary studies addressing the using SSM on speleothems have been reported (e.g., Myre et al, 2019;Feinberg et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

High spatial resolution magnetic mapping using ultra-high sensitivity scanning SQUID microscopy on a speleothem from the Kingdom of Tonga, southern Pacific

Fukuyo

Oda

Yokoyama

et al. 2020

Preprint

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Speleothems can be an ideal archive of paleomagnetism because they retain continuous geomagnetic records in stable conditions and can be used for reliable radiometric dating using U-series and radiocarbon methods. However, their weak magnetic signals hinder the widespread use of this archive in the field of geoscience. While previous studies successfully reconstructed paleomagnetic signatures, including geomagnetic excursions, their time resolutions presented were still not reached to a sufficient level. Recently emerging scanning SQUID microscopy (SSM) in this field can image very weak magnetic fields while maintaining high spatial resolution that could likely overcome this obstacle. In this study, we employed SSM to conduct paleomagnetic measurements on a stalagmite collected at Anahulu cave in Tongatapu Island, the Kingdom of Tonga. The sliced sample to a thickness of ca. 0.2 mm was scan for NRM using SSM showed the influence of viscous remanent magnetization. The average measured magnetic field after 5 mT AF demagnetization is ca. 0.27 nT with a sensor-to-sample distance of ~200 µm. A stronger magnetic field (average: ca. 0.62 nT) was observed above the grayish surface layer, as compared to that of the white inner layer (average: ca. 0.09 nT) associated with the laminated structures of a speleothem at the submillimeter scale with the SSM. The magnetization of the speleothem sample calculated by an inversion of isothermal remanent magnetization (IRM) also suggests that magnetic mineral content in the surface layer is higher than the inner layer. This feature was further investigated by low-temperature magnetometry and was suggested that it contains magnetite, maghemite, and goethite. The first-order reversal curve (FORC) measurements and the decomposition of IRM curves show that this speleothem contains a mixture of magnetic minerals with different coercivities and domain states. The contribution from maghemite and goethite to the total magnetization of the grayish surface layer is much higher than the white inner layer. The speleothem retaining magnetically and visually two distinct layers indicates that the depositional environment was shifted when the surface layer was deposited and was likely changed to the oxidative environment.

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“…It is possible to calculate with confidence the magnetization of small particles generating discrete, isolated anomalies (i.e., de Groot et al, ; Lima & Weiss, ; Weiss et al, ). Here, we investigated the small‐scale spatial variation of the remanent magnetization in large magnetite grains (>100 μm).…”

Section: Introductionmentioning

confidence: 99%

Multistep Parametric Inversion of Scanning Magnetic Microscopy Data for Modeling Magnetization of Multidomain Magnetite

Pastore

Church

McEnroe

2019

Geochem Geophys Geosyst

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Development in instrumentation and technology now allows for mapping of magnetic anomalies, caused by spatial variations in magnetization in the source material, from the mineral to the crustal anomalies scale. High‐resolution magnetic mapping techniques allow for accurate investigation of the magnetization in natural rock samples and particularly of their remanence carriers, which can record geologically meaningful information. Multidomain magnetic grains are expected to retain a remanence that is susceptible to change by exposure to magnetic fields or by changes in temperature. Although this makes multidomain grains less reliable remanence carriers for paleomagnetic studies, their magnetization contributes to rocks bulk magnetization and to induced anomalies in the Earth crust. Here, we investigate the fine‐scale magnetization of a sample that exhibits a multidomain behavior. We used a scanning magnetic microscope, equipped with a room temperature magnetic tunnel junction sensor, to map the magnetic field over a petrographic thin section of the sample containing large magnetite grains (>100 μm) surrounded by serpentine and carbonate. We modeled the fine‐scale remanent magnetization of the magnetite by inverting the magnetic scans data acquired in near‐field‐free conditions. We applied a multistep inversion, a priori tested on a synthetic model, with a controlled range on the intensity of the magnetization. Modeling results on the study sample suggest homogenously magnetized regions within the magnetite grains with variable remanent magnetization intensities and directions coherent with the multidomain behavior inferred from bulk measurements.

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Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

Cited by 43 publications

References 60 publications

Principles and techniques of the quantum diamond microscope

Principles and techniques of the quantum diamond microscope

High spatial resolution magnetic mapping using ultra-high sensitivity scanning SQUID microscopy on a speleothem from the Kingdom of Tonga, southern Pacific

Multistep Parametric Inversion of Scanning Magnetic Microscopy Data for Modeling Magnetization of Multidomain Magnetite

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