MAGNETIC-PROPERTIES OF THE MIXED SPINEL CO1-2XO4(XSIXFE2)

The structural and magnetic properties of the mixed spinel Co1+xSixFe2 -2xO4 system for 0.1 less than or equal to x less than or equal to 0.6 have been studied by means of X-ray diffraction, magnetization, and M ossbauer spectroscopy measurements. X-ray intensity calculations indic ate that Si4+ ions occupy only tetrahedral (A) sites replacing Fe3+ io ns, and the added Co2+ ions substitute for (B) site Fe3+ ions. The Mos sbauer spectra at 300 K have been fitted with two sextets in the ferri magnetic state corresponding to Fe3+ at the A and B sites, for x less than or equal to 0.3. The Mossbauer intensity data shows that Si posse sses a preference for the A site of the spinel. The variation of the s aturation magnetic moment per formula unit measured at 300 K with the Si content, is explained on the basis of Neel's collinear spin orderin g model for x less than or equal to 0.3 which is supported by Mossbaue r, and X-ray data. The Curie temperature decreases nearly linearly wit h increase of the Si content, for x = 0.1-0.6.