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Determining the magnetic attempt time τ0 , its temperature dependence, and the grain size distribution from magnetic viscosity measurements

DOI: 10.1002/2015JB012283 DOI Help

Authors: Thomas Berndt (Imperial College London) , Adrian R. Muxworthy (Imperial College London) , Greig A. Paterson (Institute of Geology and Geophysics, Chinese Academy of Sciences)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Geophysical Research: Solid Earth , VOL 120 , PAGES 7322 - 7336

State: Published (Approved)
Published: November 2015

Abstract: A new method to determine the atomic attempt time τ0 of magnetic relaxation of fine particles, which is central to rock and soil magnetism and paleomagnetic recording theory, is presented, including the determination of its temperature dependence, and simultaneously the grain size distribution of a sample. It is based on measuring a series of zero-field magnetic viscous decay curves for saturation isothermal remanent magnetization at various different temperatures that are later joined together on a single grain size scale from which the grain size distribution and attempt time are determined. The attempt time was determined for three samples containing noninteracting, single-domain titanomagnetites of different grain sizes for temperatures between 27 K and 374 K. No clear temperature-dependent trend was found; however, values varied significantly from one sample to the other: from 10−11 to 10−8s; in particular, the sample containing multiple magnetic phases had an effective attempt time significantly lower than the more homogeneous samples, thereby questioning the applicability of the simple Néel-Arhennius equation for magnetic relaxation for composite materials.

Journal Keywords: atomic attempt time; grain size distribution; magnetic viscosity; magnetic relaxation time

Subject Areas: Technique Development, Earth Science, Physics

Diamond Offline Facilities: SQUID-VSM Magnetometer (Quantum Design)
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Added On: 17/02/2016 12:40

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Technique Development - Earth Sciences & Environment Earth Sciences & Environment Physics Magnetism Geology Geophysics

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