Hausmannite Mn_3O_4 nanorods: synthesis, characterization and magnetic properties

摘要

High yield hausmannite (Mn_3O_4) nanorods with diameters of about 100 nm and lengths up to 15-20 mu m have been prepared by vacuum calcining of the precursor (Mn_3O_4 + MnOOH), which was hydrothermally prepared by the reaction of PEG-20000 and KMnO_4 at 180 deg C for 20 h. Transmission electron microscopy and the selected-area electron diffraction pattern reveal that these Mn_3O_4 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 Mn_3O_4 nanorods is 41 K, which agrees with the bulk material value, whereas the remnant magnetization and coercivity are 0.89 mu_B and 6177 Oe respectively.