A series of strontium hexaferrites (Sr-HF) compounds, doped with a low amount of manganese SrFe12-xMnxO19 (where x = 0.00, 0.03 and 0.05), were prepared by a sol-gel method. Structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM) in order to determine some basic properties such as lattice parameters and particles size. Moreover, magnetic properties of the samples were measured in a temperature range from 2 to 900 K. The results show that the transition temperature (TC) decreases from 764 to 721 K with Mn doping at x = 0.05 content. Also, temperature and doping effects on the coercivity (Hc), the remanent magnetization (Mr) and the magnetization of saturation (MS) were discussed considering the Stoner - Wohlfarth model. A slight improvement of the magnetic properties (Hc =5.56 kOe, Mr =49.99 emu/g, MS =101.9 emu/g (i.e. 19.37 µB/u.f)) for low content (x = 0.03) is evidenced, yielding to promising material for permanent magnet devices. This improvement was explained by the relationship between the microstructure and to the effective magnetic anisotropy.