Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO 3

Magnetic semiconductors are a vital component in the understanding of quantum transport phenomena. To explore such delicate, yet fundamentally important, effects, it is crucial to maintain a high carrier mobility in the presence of magnetic moments. In practice, however, magnetization often diminishes the carrier mobility. Here, it is shown that EuTiO 3 is a rare example of a magnetic semiconductor that can be desirably grown using the molecular beam epitaxy to possess a high carrier mobility exceeding 3000 cm 2 V −1 s −1 at 2 K, while intrinsically hosting a large magnetization value, 7 μ B per formula unit. This is demonstrated by measuring the Shubnikov–de Haas (SdH) oscillations in the ferromagnetic state of EuTiO 3 films with various carrier densities. Using first‐principles calculations, it is shown that the observed SdH oscillations originate genuinely from Ti 3 d ‐ t 2g states which are fully spin‐polarized due to their energetical proximity to the in‐gap Eu 4 f bands. Such an exchange coupling is further shown to have a profound effect on the effective mass and fermiology of the Ti 3 d ‐ t 2g electrons, manifested by a directional anisotropy in the SdH oscillations. These findings suggest that EuTiO 3 film is an ideal magnetic semiconductor, offering a fertile field to explore quantum phenomena suitable for spintronic applications.