Open AccessDevelopment of scanning SQUID microscope system and its applications on geological samples: A case study on marine ferromanganese crust
Author(s) -
Hirokuni Oda,
Jun Kawai,
Akira Usui,
Yuhji Yamamoto,
Atsushi Noguchi,
Isoji Miyagi,
Masatoshi Miyamoto,
Jun-ichi Fujihira,
Masahiko Sato
Publication year - 2020
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1590/1/012037
Subject(s) - squid , scanning squid microscopy , cryostat , earth's magnetic field , geology , crust , ferromanganese , microscope , signal (programming language) , sapphire , superconductivity , materials science , mineralogy , magnetic field , magnetometer , optics , geophysics , physics , condensed matter physics , gradiometer , laser , metallurgy , ecology , manganese , quantum mechanics , computer science , biology , programming language
We present developments and applications of a high resolution scanning superconducting quantum interference device (SQUID) microscope for imaging magnetic field of geological samples at room temperature. A directly coupled low-temperature SQUID with a 200 μm × 200 μm pickup loop was mounted on a sapphire rod and separated from room temperature by a sapphire window. The environmental noise of the SQUID was successfully reduced by subtracting the signal of an additional reference SQUID placed inside a cryostat. The resulting system noise level was estimated to be about 50 pT. A geological thin section could be placed on a non-magnetic sample holder with an XYZ stage for scanning in an area of 100 mm × 100 mm. The minimum achievable distance from the SQUID to the sample is measured as ∼200 µm. An application of the SSM to a marine ferromanganese crust successfully provided beautiful stripe patterns in the magnetic images. The patterns could be correlated to the history of geomagnetic field reversals. The boundaries of the magnetic polarity domains were useful guides for the estimation of the deposition age by correlation with the standard geomagnetic polarity timescale. The established age model gave an average growth rate of ∼2.7 mm/Ma, which is consistent with that obtained by radiometric dating using 10 Be (∼2.6 mm/Ma).