Investigation of super-exchange interactions in BaHoxFe12−xO19 (0.1≤x≤0.4) nanohexaferrites and exploration at ultra high frequency region

BaHoxFe12−xO19 (x=0.1, 0.2, 0.3, 0.4) nanohexaferrites were successfully synthesized for the first time by sol–gel auto-combustion technique. X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDAX) were utilized to investigate the different structural parameters and elemental composition. Incorporation of Ho3+ ions increased the dc resistivity while a decrease in the saturation magnetization (Ms), 66.68–57.08 emu/g, followed by decrease in Curie temperature (766.83–758.15 K), exchange integral (J), and anisotropy was observed. The obtained values of Ms were found to be very high as compared to the values reported in the bulk form. The dielectric constant (ε′) and dielectric loss tangent (tan δ) were investigated as a function of frequency and the behavior is explained on the basis of Maxwell–Wagner model and Koop׳s theory. Additionally, a maiden attempt was made to explore the BaHoxFe12−xO19 nanohexaferrites at ultra-high frequencies and observed ultra-low magnetic loss (0.004–0.01) and dielectric loss (0.004–0.06).