Structure and Magnetism of EuS on Bi₂Se₃(0001)

Abstract

The rocksalt‐type ferromagnetic (FM) insulator EuS (bulk TC = 17 K) grown on Bi2Se3 with well‐matched (111) plane of the film and (0001) plane of the substrate is studied. The system may feature magnetic proximity effect breaking the time‐reversal symmetry and opening a bandgap in the metallic topologically protected surface state of Bi2Se3. The experimental X‐ray diffraction studies are combined with ab initio calculations to resolve contradictory results concerning the enhancement of the TC up to 300 K and the degree of induced magnetization in the system. It is concluded that previous studies relied on idealized and unconfirmed structure models. Herein, it is shown by surface X‐ray diffraction (SXRD) with ab initio calculations that a two double layer‐thick EuS film grows with a sharp interface and without chemical intermixing in a single domain state in an FCC‐type stacking on the Bi2Se3(0001) surface in which the topmost layer is metallic, thereby lifting polarity. A large pz‐orbital‐derived top‐layer sulfur magnetic moment of 0.6 μB is found, whereas for europium, μEu = 6.9 μB throughout the film is found. No magnetization within the first Bi2Se3 quintuple layer is found. The calculation of the exchange parameters Jij indicates a complex FM and antiferromagnetic ordering between europium and sulfur with a maximum Néel temperature of 226 K.

Absence of Magnetic Proximity Effect at the Interface of Bi2Se3 and (

“…However, XMCD measurements at the Pt edges have shown no evidence of induced magnetism [47][48][49]. Theoretical studies using first-principles calculations show insignificant or no magnetism in the TI for Bi 2 Se 3 =EuS with ideally sharp interfaces [17,18,50], which is consistent with our XMCD results. Instead, Eu doping on Bi 2 Se 3 could result in local magnetic moments that are much larger than those induced by the adjacent magnetic layer, possibly explaining the experimental observations [17].…”

Emergence of threefold symmetric helical photocurrents in epitaxial low twinned Bi 2 Se 3

“…The large bulk energy gap of 3.1 eV makes the EuS layer transparent to the 1.55-eV excitation laser. Additionally, at room temperature, EuS on Bi 2 Se 3 has been conclusively demonstrated to be a nonmagnetic dielectric and therefore no intrinsic time-reversal symmetry-breaking effects are anticipated to contribute to the experiment ( 47 ).…”

Progress and prospects in the quantum anomalous Hall effect

“…Extraordinary care is warranted in the TI growth, and the magnetic interfacial heterostructuring thereafter, to properly mitigate the adverse influence from residual chalcogen atoms since optimal TI demands a Se/Te-rich growth condition. This intriguing discovery has opened a vibrant arena for proximitized MI/TI heterostructures [110][111][112][113][114][115][116][117][118][119][120][121].…”