MAGNETISM AND CATION DISTRIBUTION IN IRON ZINC SILICATES

Silicates in the Fe2-xZnxSiO4 system are known to give a limited solution series [1] with the olivine structure on the iron side (end-member fayalite) and phenakite structure on the zinc side (end-member willemite). To obtain information about the magnetic structure and cation distribution, synthetic powder samples in this series (x = 0.2, x = 1.4) have been investigated by neutron diffraction. The fayalite sample (x = 0.2) gives magnetic diffraction patterns below the Neel temperature (similar to 56 K). On the M1 site spin canting (with respect to the b-axis) of 41 degrees and 16 degrees and magnetic moments of 4.2 mu(B) and 2.4 mu(B) are found at 2 K and 40 K, respectively. The spin canting on the M2 site, supposed from Mossbauer measurements [2], could not be confirmed. The magnetic moment is 4.0 mu(B) and 3.6 mu(B), at 2 K and 40 K, respectively. Zinc clearly prefers the M1 lattice site. In the willemite sample (x = 1.4), a small superimposed intensity at 2 K could indicate the magnetic order as expected, based on magnetically split Mossbauer spectra [2] Zinc prefers the Zn1 site.