Imperial College London
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Professor Adrian Muxworthy

Faculty of Engineering, Department of Earth Science & Engineering

Professor of Earth and Planetary Magnetism
 
 
 
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Contact

 

+44 (0)20 7594 6442adrian.muxworthy

 
 
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Location

 

4.48Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Muxworthy:2002,
author = {Muxworthy, AR and Dunlop, DJ},
journal = {EARTH PLANET SC LETT},
pages = {369--382},
title = {First-order reversal curve (FORC) diagrams for pseudo-single-domain magnetites at high temperature},
url = {http://hdl.handle.net/10044/1/850},
volume = {203},
year = {2002}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The recently developed first-order reversal curve (FORC) technique for rapidly examining magnetic domain state has great potential for paleomagnetic and environmental magnetic investigations. However, there are still some gaps in the basic understanding of FORC diagrams, in particular the behavior of pseudo-single-domain (PSD) grains and the contribution of magnetostatic interactions. In this paper we address some of these problems. We report the first FORC diagrams measurements on narrowly sized and well-characterized synthetic PSD through multidomain (MD) magnetite samples. The FORC diagrams evolve with grain size from single-domain (SD)-like to MD-like through the PSD grain size range. Since each sample contains grains of essentially a single size, individual PSD grains evidently contain contributions from both SD-like and MD-like magnetic moments, in proportions that vary with grain size; the evolving FORC diagrams cannot be due to physical mixtures of SD and MD grains of widely different sizes. The FORC diagrams were all asymmetric. Small PSD samples have FORC diagrams with a distinctive closed-contour structure. The distributions of the larger MD grains display no peak, and lie closer to the interaction-field axis. To assess the effect of magnetostatic interactions, we measured FORC diagrams between room temperature and the Curie temperature. On heating the FORC distributions contract without changing shape until similar to500degreesC. Above this temperature the diagrams become more MD-like, and in addition become more symmetric. The temperature dependence of the interaction-field parameter is proportional to that of the saturation magnetization, in accordance with Neel's interpretation of the Preisach diagram. The decrease in asymmetry with heating suggests that the origin of the asymmetry lies in magnetostatic interactions. The magnetic hysteresis parameters as a function of temperature were determined from the FORC curves. As the grain size decreased the no
AU  - Muxworthy,AR
AU  - Dunlop,DJ
EP  - 382
PY  - 2002///
SN  - 0012-821X
SP  - 369
TI  - First-order reversal curve (FORC) diagrams for pseudo-single-domain magnetites at high temperature
T2  - EARTH PLANET SC LETT
UR  - http://hdl.handle.net/10044/1/850
VL  - 203
ER  -
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