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Direct observation of the thermal demagnetization of magnetic vortex structures in nonideal magnetite recorders
Author(s) -
Almeida Trevor P.,
Muxworthy Adrian R.,
Kovács András,
Williams Wyn,
Nagy Leslei,
Conbhuí Pádraig Ó,
Frandsen Cathrine,
Supakulopas Radchagrit,
DuninBorkowski Rafal E.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl070074
Subject(s) - magnetite , demagnetizing field , thermomagnetic convection , remanence , vortex , materials science , condensed matter physics , rock magnetism , curie temperature , thermal , particle (ecology) , geology , mineralogy , nuclear magnetic resonance , magnetic field , magnetization , physics , ferromagnetism , thermodynamics , metallurgy , oceanography , quantum mechanics
Abstract The thermal demagnetization of pseudo‐single‐domain (PSD) magnetite (Fe 3 O 4 ) particles, which govern the magnetic signal in many igneous rocks, is examined using off‐axis electron holography. Visualization of a vortex structure held by an individual Fe 3 O 4 particle (~250 nm in diameter) during in situ heating is achieved through the construction and examination of magnetic‐induction maps. Stepwise demagnetization of the remanence‐induced Fe 3 O 4 particle upon heating to above the Curie temperature, performed in a similar fashion to bulk thermal demagnetization measurements, revealed that its vortex state remains stable under heating close to its unblocking temperature and is recovered upon cooling with the same or reversed vorticity. Hence, the PSD Fe 3 O 4 particle exhibits thermomagnetic behavior comparable to a single‐domain carrier, and thus, vortex states are considered reliable magnetic recorders for paleomagnetic investigations.