Magnetic and microstructural properties of Al substituted M-type Ca–Sr hexaferrites

• Al substituted M-type Ca–Sr hexaferrites were prepared by the conventional ceramic techniques.
• The magnetic powders with Al content (x) from 1.0 to 1.4 consists of pure magnetoplumbite.
• The saturation magnetization (Ms) linearly decreases with Al content (x) from 0 to 1.4.
• The coercivity (Hc) increases with Al content (x) from 0 to 1.4.

In the current study, Al substituted M-type Ca–Sr hexaferrites, with composition Ca0.6Sr0.1La0.3Fe12−xAlxO19 (0≤x≤1.4), have been prepared using the conventional ceramic techniques. The phase composition of the magnetic powders was characterized by X-ray diffraction (XRD). The XRD data show that the magnetic powders with Al content (x) from 0 to 0.8 show α-Fe2O3 as a second phase, while the magnetic powders with x from 1.0 to 1.4 consist of pure magnetoplumbite without any other impurity phases. A field emission scanning electron microscopy (FE-SEM) was used to observe the morphologies of the magnetic powders. FE-SEM images of the magnetic powders show the hexagonal platelet-like shape. The magnetic properties of the magnetic powders were measured by a physical property measurement system-vibrating sample magnetometer (PPMS-VSM). The saturation magnetization (Ms) linearly decreases with Al content (x) from 0 to 1.4. While the remanent magnetization (Mr) first increases with Al content (x) from 0 to 0.2 and then decreases when Al content (x)≥0.2. However, the coercivity (Hc) increases with Al content (x) from 0 to 1.4.