Incipient antiferromagnetism in the Eu-doped topological insulator Bi${}_2$Te${}_3$

Abstract

Rare earth ions typically exhibit larger magnetic moments than transition metal ions and thus promise the opening of a wider exchange gap in the Dirac surface states of topological insulators. Yet, in a recent photoemission study of Eu-doped Bi${}_2$Te${}_3$ films, the spectra remained gapless down to $T=20\text{K}$. Here, we scrutinize whether the conditions for a substantial gap formation in this system are present by combining spectroscopic and bulk characterization methods with theoretical calculations. For all studied Eu doping concentrations, our atomic multiplet analysis of the $M_{4,5}$ x-ray absorption and magnetic circular dichroism spectra reveals a Eu${}^{2+}$ valence and confirms a large magnetic moment, consistent with a $4f^7{}^8{S}_{7/2}$ ground state. At temperatures below $10\text{K}$, bulk magnetometry indicates the onset of antiferromagnetic (AFM) ordering. This is in good agreement with density functional theory, which predicts AFM interactions between the Eu impurities. Our results support the notion that antiferromagnetism can coexist with topological surface states in rare-earth doped Bi${}_2$Te${}_3$ and call for spectroscopic studies in the kelvin range to look for novel quantum phenomena such as the quantum anomalous Hall effect.

15 pages, 9 figures

References in corpus (6)

• High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator
• Precise quantization of anomalous Hall effect near zero magnetic field
• Chemical potential dependent gap-opening at the Dirac surface states of Bi2Se3 induced by aggregated substitutional Cr atoms
• Scaling of the Quantum Anomalous Hall Effect as an Indicator of Axion Electrodynamics
• Impurity states in the magnetic topological insulator V:(Bi,Sb)${}_2$Te${}_3$
• Intercalated europium metal in epitaxial graphene on SiC

Cited by in corpus (8)

• Antiferromagnetic VdW Phase at the Interface of Sputtered Topological Insulator/Ferromagnet-Bi2Te3/Ni80Fe20 Heterostructures
• Valence state determines the band magnetocrystalline anisotropy in 2D rare-earth/noble-metal compounds
• Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures
• Experimental demonstration of a magnetically induced warping transition in a topological insulator mediated by rare-earth surface dopants
• Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator
• Low-energy modeling of three-dimensional topological insulator nanostructures
• Magnetic interactions of 4$f$ electrons in the topological insulator chalcogenide Bi${}_2$Se${}_3$
• Pre-Patterned Superconducting Contacts for Clean Superconductor-Topological Material Interfaces Enabling Long-Range Josephson Coupling