Preparation of <i>B</i>-site Mn-doped Spinel Fe(Al_1−<i>x</i>Mn_<i>x</i>)₂O₄ (0 ≤ <i>x</i> ≤ 0.9) Ferrite Powders using a Modified Citric Acid Route

Abstract

Preparation of spinel Mn-doped Fe(Al 1−x Mn x ) 2 O 4 (0 ≤ x ≤ 0.9) ferrite powders, in which B-site Al 3+ were replaced partially by Mn 3+ , has been tried via a modified citric acid route. Fe and Al nitrate salts and fine MnO 2 powder were used as starting materials. Homogeneous mixed solutions containing Fe 3+ , Al 3+ ions and MnO 2 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 × 10 3 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(Al 1−x Mn x ) 2 O 4 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.