Abstract
With molecular beam epitaxy, we grew uniformly vanadium-doped Bi2Se3 films which exhibit ferromagnetism with perpendicular magnetic anisotropy. A systematic study on the magneto-transport properties of the films revealed the crucial role of topological surface states in ferromagnetic coupling. The enhanced ferromagnetism with reduced carrier density can support quantum anomalous Hall phase in the films, though the anomalous Hall resistance is far from quantization due to high carrier density. The topological surface states of films exhibit a gap of ∼180 meV which is unlikely to be magnetically induced but may significantly influence the quantum anomalous Hall effect in the system.
Highlights
Ferromagnetic topological insulators (TIs) exhibiting these effects could be used to develop new-concept electronic and spintronic applications.[5,6]. The explorations in this direction were greatly encouraged by the experimental realization of ferromagnetism and quantum anomalous Hall effect (QAHE) in magnetically doped three-dimensional (3D) TI films.[3]
Gap-opening at the Dirac surface states induced by magnetic impurities were reported in several studies on magnetically doped Bi2Se3, but the ferromagnetism and anomalous Hall effect (AHE) observed are always weak.[11,12,13]
To understand the mechanism of the ferromagnetism in V-doped Bi2Se3 and its relationship with the electronics structure, we studied the thickness-dependent transport properties of Bi1.97V0.03Se3 films because the evolution of the band structure of Bi2Se3 with thickness has been mapped in detail by angle-resolved photoemission spectroscopy (ARPES).[20]
Summary
Ferromagnetism can induce novel phenomena in topological insulators (TIs) such as the quantum anomalous Hall effect (QAHE) and topological magneto-electric effect.[1,2,3,4] Ferromagnetic TIs exhibiting these effects could be used to develop new-concept electronic and spintronic applications.[5,6] The explorations in this direction were greatly encouraged by the experimental realization of ferromagnetism and QAHE in magnetically doped three-dimensional (3D) TI films.[3]. Ferromagnetism in vanadium-doped Bi2Se3 topological insulator films
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