Magnetic polaron and unconventional magnetotransport properties of the single-crystalline compound EuBiTe3

Abstract

We investigate the magnetic, thermal, and electrical transport properties on the single-crystalline compound ${\mathrm{EuBiTe}}_{3}$. The magnetization measurements reveal the antiferromagnetic transition at 7 K along the $ab$ plane with a stable ${\mathrm{Eu}}^{2+}$ ion. A short-range ferromagnetic interaction along the $c$ axis is inferred from magnetic susceptibility and heat capacity measurements, which we associate with the presence of magnetic polarons. The magnetic polaron gives rise to unconventional negative magnetoresistance such as the weak antilocalization (WAL) and weak localization crossover. The WAL of the angle-resolved magnetoconductivity is well described by the Al'tshuler and Aronov model along the longitudinal magnetoconductivity. The magnetic polaron is widely observed above N\'eel temperature up to 50 K, which is supported by the Majumdar-Littlewood model in a scaled magnetoresistance. Even though ${\mathrm{EuBiTe}}_{3}$ should have one hole per formula unit, the electrical conductivity $\ensuremath{\sigma}(T)$ exhibits strong localized insulating behavior. The transport mechanism of $\ensuremath{\sigma}(T)$ is distinguished by two different mechanism: Efros-Shklovskii-type variable range hopping (VRH) transport in the high-temperature range ($T\phantom{\rule{0.16em}{0ex}}\ensuremath{\ge}\phantom{\rule{0.16em}{0ex}}52$ K) and three-dimensional VRH transport in the low-temperature regime ($T\ensuremath{\le}$ 50 K). The VRH transport suggests that the insulating behavior of $\ensuremath{\sigma}(T)$ on the compound can originate from a Mott-type insulator with strong Coulomb interaction.