Structural and Magnetic Properties of Sn4+ Doped Strontium Hexaferrites Prepared via Sol–Gel Auto-Combustion Method

Sn-Zn-Co-substituted strontium M-type hexaferrite SrZn
_x
Co
_x
Sn
_2x
Fe
_12-4x
O
₁₉
(x = 0.0, 0.3, 0.5, and 0.7) was synthesized via modified sol-gel auto-combustion method. A microwave device was used to obtain the finest particles and to complete the combustion process. By substitution of tetravalent and divalent cations instead of iron, magnetic and structural properties of M-type hexaferrite were changed. So, the effects of Sn
⁴⁺
, Zn
²⁺
, and Co
²⁺
doping on the structure and magnetic characterization of M-type hexaferrite were investigated. The Fourier transform infrared spectroscopy revealed bands at 430 and 590 cm
^-1
, related to the stretching vibrating bonds of Fe-O. The X-ray diffraction analysis showed that all samples prepared were of P6
₃
/mmc symmetry and average crystal size of 68 nm. Field emission scanning electron microscopy analysis revealed the hexagonal plateletlike shape of all samples. Vibrating sample magnetometer results showed that by increasing the dopants content, coercivity (H
_c
), and saturation magnetization (M
_s
) changed drastically. Saturation magnetizations decreased during dopants displacement and then reach to the highest value (65.46 emu/g) at x = 0.5 then increasing of dopants to x = 0.7, cause the reduction of M
_s
(56.13 emu/g). Coercivity diminished by dopant substitution and the semi-hard samples were received as an alternative to the hard hexaferrite.