Hausmannite Mn₃O₄nanorods: synthesis, characterization and magnetic properties

High yield hausmannite (Mn3O4) nanorods with diameters of about 100 nm and lengths up to 15–20 µm have been prepared by vacuum calcining of the precursor (Mn3O4+MnOOH), which was hydrothermally prepared by the reaction of PEG-20000 and KMnO4 at 180 °C for 20 h. Transmission electron microscopy and the selected-area electron diffraction pattern reveal that these Mn3O4 nanorods show single-crystal growth along the [100] direction. The PEG-20000 and the calcination conditions have key effects on the morphology and phase purity of the product. Magnetism measurements show that the blocking temperature for these Mn3O4 nanorods is 41 K, which agrees with the bulk material value, whereas the remnant magnetization and coercivity are 0.89 μB and 6177 Oe respectively.