We investigate the relation between lattice, vibrational, and electrical changes in Ru/ Re-doped M-type barium hexaferrite, ${\mathrm{BaFe}}_{11.9}{(\mathrm{Ru},\mathrm{Re})}_{0.1}{\mathrm{O}}_{19}$. Temperature-dependent x-ray diffraction shows only a few weak extra reflections associated with the minor $\alpha \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$ phase, with no temperature-induced change in the BaM crystal structure. However, the lattice parameters and unit-cell volume change their thermal-expansion behavior between 390 and 420 K. Raman spectroscopy shows a complementary local response, with two selected Fe-O modes, assigned to mixed ${\mathrm{FeO}}_6$ octahedral vibrations and ${\mathrm{FeO}}_5$ bipyramidal vibrations, displaying shallow nonmonotonic shifts near 380–400 K. At higher temperatures, the electrical measurements reveal a systematic change in charge dynamics. The phase map obtained from the loss tangent changes from a capacitivelike response toward a stronger resistive contribution, while the real part of the ac conductivity, ${\sigma }_{\mathrm{ac}}^{\prime }\left(T\right)$, develops a clearer frequency dependence above about 480 K. Effective Arrhenius fits in the 293–483 K interval yield frequency-dependent activation energies and preexponential factors that follow a Meyer-Neldel-like relation, with $E_{\mathrm{MN}}=(41.0\pm 0.5)\mathrm{meV}$ and $T_{\mathrm{MN}}=(476\pm 6)\mathrm{K}$. The value of $E_{\mathrm{MN}}$ is close to the phonon energy of the Raman mode near $335{\mathrm{cm}}^{-1}, E_{\mathrm{ph}}\approx 41.5\mathrm{meV}$, associated with mixed ${\mathrm{FeO}}_6$ octahedral vibrations. The structural, vibrational, and electrical results therefore indicate that the previously reported semiconductor-to-metal crossover is accompanied by small changes in the local Fe-O environment. The comparable vibrational and Meyer-Neldel energy scales are consistent with a possible contribution of phonon-assisted hopping involving the ${\mathrm{FeO}}_6$ octahedral network.

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• Electrical properties
• Ferrites
• Raman spectroscopy
• X-ray diffraction