A series of Mn substituted M-type hexaferrites having the chemical compositions of Sr0.75La0.25Fe12.00-xMnxO19 (where 0.00 ≤ x ≤ 0.60) were prepared by the conventional ceramic processing method. X-ray diffraction (XRD) was used to evaluate the hexagonal phase evolution for the M-type hexaferrite magnetic powders. The XRD results show that Mn3+ ions completely enter into the hexaferrite structure and all magnetic powders show M-type hexagonal structure. Magnetic properties of the powders were studied by a physical property measurement system-vibrating sample magnetometer (PPMS-VSM). The saturation magnetization (Ms) and remanent magnetization (Mr) first slightly increase with Mn content (x) from 0.00 to 0.24, and then decrease with Mn content (x) form 0.24 to 0.60. The coercivity (Hc) of the magnetic powders first increases with Mn content (x) from 0.00 to 0.12, and then decrease with Mn content (x) form 0.12 to 0.36, and increases with the increase of Mn content (x) when Mn content (x) ≥ 0.36.

Keywords: Hexagonal ferrites, Mn substitution, X-ray diffraction, Magnetic properties.