Fe(NO3)3•9H2O, Sr(NO3)2 and different amounts of citric acid were used as crude materials to form sol in the solution. The sol grew on the surface of the absorbent cotton template to form gel. The strontium ferrite microtubules were prepared after the calcination process. The phase, morphology, particle diameter, and magnetic properties of samples were detected by XRD, SEM, TEM and VSM. It was found that the microtubule external diameters were between 8 and 13 μm, the wall thickness was between 0.5 and 2 μm. The addition of citric acid led to the fragmentation of microtubules, and there were many holes on the pipe wall. The specific area increased. As the increase of the citric acid content, the coercive force and the saturation magnetization of the samples increased firstly, and then decreased. As the mole ratio of citric acid to the metal ion was 1∶1, and the calcination temperature was 850 ℃, the coercive force, the saturation magnetization and residual magnetization of the samples were 7115.1 Oe, 70.1 emu/g and 42.4 emu/g respectively. The microtubule formation mechanism and the effect on the magnetic properties were studied systemically also.

Key words: SrFe12O19, microtubule, absorbent cotton, citric acid