Spin correlation studies of FeF<sub>2</sub> and Fe<sub>0.6</sub>Zn<sub>0.4</sub>F<sub>2</sub> by optical exciton-magnon transitions
W Kleemann; R Uhlig; W Kleemann; Angewandte Phys., Duisburg Univ., West Germany; R Uhlig; Angewandte Phys., Duisburg Univ., West Germany
Журнал:
Journal of Physics: Condensed Matter
Дата:
1989-03-06
Аннотация:
The fine structure and the temperature dependence of the moments M<sub>0</sub>, M<sub>1</sub> and M<sub>2</sub> of a sharp and isolated exciton-magnon absorption line near lambda =465 nm are studied on FeF<sub>2</sub> and Fe<sub>0.6</sub>Zn<sub>0.4</sub>F<sub>2</sub>. The results compare well with theoretical predictions of Tanabe and co-workers, since overlap with other magnon or phonon sidebands is nearly negligible. All moments show cusp-like behaviour at T<sub>N</sub> owing to singularities of the spin correlation functions involved. In Fe<sub>0.6</sub>Zn<sub>0.4</sub>F<sub>2</sub> additional precursor peaks arise at T approximately=1.2 T<sub>N</sub>. They are attributed to enhanced short-range order characteristic of reduced dimensionality.
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