Magnetic and transport properties of electron doped EuTiO₃ thin films with La³⁺ (4f⁰) or Gd³⁺ (4f⁷) donors grown by gas source molecular beam epitaxy

EuTiO3 (ETO) is a unique magnetic semiconductor with a large localized magnetic moment of Eu2+ (4 f 7). By the doping of high-mobility electrons in the Ti 3 d conduction band, peculiar magnetotransport properties such as the unconventional anomalous Hall effect (AHE) due to Berry curvature in momentum space, as well as the Shubnikov–de Haas oscillations of spin polarized electrons, have been observed. In this study, we have examined the physical properties of high quality ETO films with La3+ (4 f0) or Gd3+ (4 f7) donors (ELTO or EGTO) grown on nearly lattice matched SrTiO3 substrates with a gas source molecular beam epitaxy. We find that the anti-ferromagnetic ordering of ELTO is destabilized by the vacancy of the magnetic moment on the La-site for ELTO. The maximum electron mobility for ELTO (<3200 cm2 V−1 s−1) is larger than that of EGTO (<1500 cm2 V−1 s−1), keeping the metallic state at very diluted doping. The AHE changes its sign with shifting the Fermi level position across the Weyl nodes, as seen previously for compressively strained ELTO films, but the critical electron density is much lower, which can be explained by the absence of additional crystal-field splitting in the lattice matched system. These unveiled transport properties provide deeper understanding of the transport phenomena related to the topology of the band structure in high-mobility, magnetic oxide semiconductors.