Thin films of BaFe 12 O 19 have been grown on (00l) oriented α-Fe 2 O 3 single crystal substrates. The initial stages of the reaction between BaFe 2 O 4 thin films and hematite single crystals have been investigated using AFM and SEM. The microstructure studies showed that (00l) oriented BaFe 12 O 19 microcrystallites formed during annealing at 900–1100°C. It was concluded that the surface diffusion had a dominating role in formation of thin BaFe 12 O 19 films. Crystal growth was performed by stacking of layers with the thickness 2.3nm, correlated with the c-parameter of the BaFe 12 O 19 unit cell.