Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract The cation distribution in the synthetic samples of olivine-type structure with composition (Fe x Mn1−x )2SiO4 was determined at room temperature and confirms previous Mössbauer results. At low temperature an antiferromagnetic ordering is observed. The magnetic structures can be described in the crystallographic cell (i.e. k=0). They are interpreted on the basis of the irreducible representations (modes) of the symmetry groups which are compatible with Pnma. The dominant modes observed for all compounds, including Fe2SiO4 and Mn2SiO4, only differ in their direction. The main direction of magnetization is dominated by the Fe2+ single-ion anisotropy. At 4.2K, for x=0.29, it is parallel to the c-axis, whereas for x=0.76 the direction is parallel to the b-axis. The anisotropy of the M1-sites dominates in the first case, whereas M2-anisotropy dominates in the second case. The influence of temperature is demonstrated for x=0.50 where c is the main direction at 4.2K, when it is b at 38K.
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