Structural and Magnetic Properties of (Mn, Cr)xCo(1-x)Fe(2)O(4) Thin Films Prepared by Sol-gel Method

By substituting Mn or Cr for Co in inverse spinel CoFe2O4, MnxCo1-x Fe2O4 and CrxCo1-xFe2O4 thin films were prepared by sol-gel method and their structural and magnetic properties were investigated. X-ray diffraction indicates that the cubic lattice constant increase for the Mn substitution while it hardly changes for the Cr substitution. Substitution of Mn 2 for octahedral Co2+ sites can explain the increase of lattice constant in MnxCo1-x Fe2O4. On the other hand, Substitution of Cr3+ for octahedral Co2+ and subsequent reduction of Fe3+ ion into Fe z+ are expected to happen. Mdssbauer spectroscopy measurements on CrxCo1-xFe2O4 indicate the existence of tetrahedral Fez 2 ions that are created through reduction of tetrahedral Fe3+ ions in order to compensate charge imbalance happened by Cr3+ substitution for octahedral Co2+ sites. On the other hand, no Fe2+ ions were detected by Mossbauer spectroscopy for MnxCo1-xFe2O4. A migration of Fe3+ ions from octahedral to tetrahedral sites in MnxCo1-xFe2O4 was detected by Mbssbauer spectroscopy for x>0.47. Vibrating sample magnetometry measurements on the samples at room temperature revealed that the saturation magnetization increases by Mn and Cr substitution for certain range of x, qualitatively explainable in terms of the comparison of spin magnetic moment among the related transition-metal ions.