Unconventional transport properties of the itinerant ferromagnet EuTi1−xNbxO3(x=0.10–0.20)

The detailed analysis of resistivity $(\ensuremath{\rho})$ for single-crystalline ${\mathrm{EuTi}}_{1\ensuremath{-}x}{\mathrm{Nb}}_x{\mathrm{O}}₃\phantom{\rule{4pt}{0ex}}(x=0.10$--0.20), an itinerant ferromagnet with very low Curie temperature $({T}_C)$, reveals that the charge conduction in this system is extremely sensitive to Nb concentration and dominated by several scattering mechanisms. Well below ${T}_C$, where the spontaneous magnetization follows Bloch's ${T}^3/2$ law, $\ensuremath{\rho}$ exhibits ${T}²$ dependence with a large coefficient $(\ensuremath{\sim}{10}^{\ensuremath{-}1}\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}$ cm ${\mathrm{K}}^{\ensuremath{-}2})$ due to the electron-magnon scattering. Remarkably, all the studied samples exhibit a unique resistivity minimum at $T={T}_{\mathrm{min}}$, below which $\ensuremath{\rho}$ shows a logarithmic increment with $T$ (for ${T}_{\mathrm{C}}<T<{T}_{\mathrm{min}})$ due to the Kondo scattering of $4{d}¹$ itinerant electrons of Nb by the localized $4f$ moments of ${\mathrm{Eu}}²⁺$ which suppresses strongly with applied magnetic field. In the paramagnetic state, ${T}²$ and ${T}^3/2$ dependence of the resistivity have been observed, suggesting an unusual crossover from a Fermi-liquid to a non-Fermi-liquid behavior with increasing $T$.