The inadequacy of applied-field Mossbauer spectroscopy as a means of proving the existence of speromagnetism
Q A Pankhurst; R J Pollard; Q A Pankhurst; Dept. of Phys. Liverpool Univ., UK; R J Pollard; Dept. of Phys. Liverpool Univ., UK
Журнал:
Journal of Physics: Condensed Matter
Дата:
1993-09-27
Аннотация:
The authors reply to the suggestion that a two-sublattice collinear spin model employed by them 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. The authors note that the value of the anisotropy constant obtained for antiferromagnetic goethite ( alpha -FeOOH) using the collinear model, K<sub>1</sub> approximately=3*10<sup>5</sup> J m<sup>-3</sup>, is constant 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*10<sup>5</sup> J m<sup>-3</sup>. The anisotropy constants of three reputedly speromagnetic insulators, calculated using the collinear model, fall within this range, and are therefore not impossibly large. The authors 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.
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