Magnetic properties of the mixed spinel Co1+xSnxFe2-2xO4

The structural and magnetic properties of the mixed spinel Co1+xSnxFe2-2xO4 system for 0.1 less than or equal tox less than or equal to0.5 have been s tudied by means of X-ray diffraction, magnetization, a.c. susceptibility an d Mossbauer effect measurements. X-ray intensity calculations indicate that Sn4+ ions occupy only octahedral (B) sites replacing Fe3+ ions and the add ed Co2+ ions substitute for A-site Fe3+ ions. The lattice constants are det ermined and the applicability of Vegard's law has been tested. The Mossbaue r spectra at 300 K have been fitted with two sextets in the ferrimagnetic s tate corresponding to Fe3+ at tetrahedral (A) and octahedral (B) sites for x less than or equal to0.4. The Mossbauer intensity data show that Sn posse sses a preference for the B-site of the spinel. As expected, the hyperfine field and Curie temperature determined from a.c. susceptibility decreases w ith increasing Sn content. The variation of the saturation magnetic moment per formula unit measured at 77 and 300 K with Sn content is satisfactorily explained on the basis of Neel's collinear spin ordering model for x=0.1-0 .4.