2017 年 64 巻 7 号 p. 383-391
Preparation of spinel Mn-doped Fe(Al1−xMnx)2O4 (0 ≤ x ≤ 0.9) ferrite powders, in which B-site Al3+ were replaced partially by Mn3+, has been tried via a modified citric acid route. Fe and Al nitrate salts and fine MnO2 powder were used as starting materials. Homogeneous mixed solutions containing Fe3+, Al3+ ions and MnO2 were added to the mixed solution of citrate acid (CA) and ethylene glycol (EG) at room temperature with stirring. After boiling and continuous drying, thus obtained precursors were heated in air to burn out the organic substances and calcined at 1173 K (900°C) for 7.2 × 103 s (2 h) under nitrogen atmosphere with a small amount of hydrogen to control the valances of Fe and Mn in the ferrite powders. Single spinel B-site Mn-doped Fe(Al1−xMnx)2O4 powders with the compositions of x = 0.0, 0.2, and 0.6 ~ 0.9 have been obtained. With increasing x value, the magnetic property of spinel powder changed from paramagnetism (x = 0) to ferrimagnetism (x = 0.2, 0.6 ~ 0.9) at room temperature. Neutron-diffraction analysis measured at room temperature proved that some of Mn ions occupied B-site and on the contrary Fe did A-site. Magnetic properties also supported this configuration determined by XRD and NRD.
