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THE INADEQUACY OF APPLIED-FIELD MOSSBAUER-SPECTROSCOPY AS A MEANS OF PROVING THE EXISTENCE OF SPEROMAGNETISM

PANKHURST, QA; POLLARD, RJ; (1993) THE INADEQUACY OF APPLIED-FIELD MOSSBAUER-SPECTROSCOPY AS A MEANS OF PROVING THE EXISTENCE OF SPEROMAGNETISM. J PHYS-CONDENS MAT , 5 (39) 7301 - 7306.

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Abstract

We reply to the suggestion that a two-sublattice collinear spin model employed by us to analyse applied-field Mossbauer spectra of various insulators yields impossibly large values for the uniaxial anisotropy constant and should therefore be disregarded in favour of a model of speromagnetism. We note that the value of the anisotropy constant obtained for antiferromagnetic goethite (alpha-FeOOH) using the collinear model, K1 congruent-to 3 x 10(5) J m-3, is consistent with both spin-flop measurements on bulk goethite and with independent theoretical calculations. The anisotropy constants of samples of the disordered iron oxyhydroxide feroxyhite (delta'-FeOOH), obtained with the collinear model, may be as high as approximately 10 X 10(5) j m-3. The anisotropy constants of three reputedly speromagnetic insulators, calculated using the collinear model, fall within this range, and are therefore not impossibly large. We reaffirm that there remains a fundamental misconception in the belief that applied-field Mossbauer spectroscopy may be employed to distinguish between speromagnetism and antiferromagnetism in randomly aligned particles and disordered materials.

Type: Article
Title: THE INADEQUACY OF APPLIED-FIELD MOSSBAUER-SPECTROSCOPY AS A MEANS OF PROVING THE EXISTENCE OF SPEROMAGNETISM
Keywords: FINE-PARTICLE GOETHITE, MAGNETIC-PROPERTIES, FERRIC GEL, FERRIHYDRITE, ANISOTROPY, TEMPERATURE, SPECTRA, POWDERS, ORDER, FEOOH
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: http://discovery.ucl.ac.uk/id/eprint/59425
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