Effect of 10 MeV electron irradiation on structural and magnetic properties of Ti- and Al- substituted strontium hexaferrite SrFe11.3Ti0.4Al0.3O19

The irradiation stability of Ti- and Al-substituted SrFe _11.3Ti _0.4Al _0.3O ₁₉ strontium hexaferrite to 10 MeV electron irradiation with the fluences of 10 ¹⁴ and 2·10 ¹⁷ cm ⁻² was investigated using various characterization techniques such as scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectrum microanalysis, atomic force microscopy, Raman spectroscopy, vibrating sample magnetometry and magnetic force microscopy. Notable changes in lattice vibrations, magnetic domain microstructure and magnetization behavior were obtained after the electron irradiation with the fluence of 2·10 ¹⁷ cm ⁻². Phonon hardening observed by Raman spectroscopy confirms the increasing disorder in crystalline structure and the presence of spin-phonon coupling in the samples after electron irradiation with the fluence 2·10 ¹⁷ cm ⁻². It was found that the strongest spin-phonon interactions correspond to A _{1 g} vibration modes at trigonal bipyramidal 2b, 2a octahedral, 4f1 tetrahedral sites and E _{1 g} mode at 4f2 octahedral site in electron-irradiated SrFe _11.3Ti _0.4Al _0.3O ₁₉ hexaferrite, while the most radiation-resistant phonon mode is A _{1 g} vibration of the Fe–O bonds at the 4f2 octahedral site. No significant change was observed in magnetic saturation magnitude after electron irradiation. The increase in coercivity and significant decrease of magnitude of the dM/dH derivative of magnetization curves with increasing radiation fluence is attributed to the increase in uniaxial magnetic-crystalline anisotropy. It is found that the fractal dimension of hierarchical magnetic domain structure in SrFe _11.3Ti _0.4Al _0.3O ₁₉ continuously decreases with increasing fluence of 10 MeV electron irradiation, which can be caused by the distortion in uniaxial magnetocrystalline anisotropy and irradiation-induced defects.