Electronic properties of GdxBi2−xSe3 single crystals analyzed by Shubnikov-de Haas oscillations

Abstract

Magnetically doped topological insulators have been significantly researched for unlocking the nontrivial topological phases and the resultant potential applications for spintronics. We report the effect of antiferromagnetic order induced by Gd substitution on the electronic properties of GdxBi2−xSe3 single crystals by analyzing the Shubnikov-de Haas oscillations. Antiferromagnetic order of Gd ions affects the 2D surface state in Bi2Se3 and changes the effective mass and lifetime of charge carriers. These observations suggest a strong correlation of 2D surface electrons with the antiferromagnetic ordering, where the itinerant electrons are bound to the Gd ions to mediate the antiferromagnetic interaction.

Dirac gap opening and Dirac-fermion-mediated magnetic coupling in antiferromagnetic Gd-doped topological insulators and their manipulation by synchrotron radiation

“…6S . Both measurements testify to the bulk AFM coupling at low temperatures that correlates with the results published in the literature for different RE-doped TIs 29 , 36 , 38 , 42 .

Figure 6 The temperature dependence of the magnetic susceptibility ( χ ) measured for Bi 1.09 Gd 0.06 Sb 0.85 Te 3 with external magnetic field applied perpendicular the surface with approximation by the Curie-Weiss law at low temperatures (red lines).

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“…These observations support the assumption of the surface Dirac-fermion-mediated magnetic coupling (via the TSS) developed in Bi 1.09 Gd 0.06 Sb 0.85 Te 3 manifesting itself in a weak hysteresis loop in the SQUID measurements, by the mid-gap semiconducting behavior of electrical resistance and the opening gap at the DP in the ARPES measurements. At temperatures above 100 K the electrical resistance first drops sharply and then increases again between 150 and 250 K demonstrating a metallic-like slow growth characteristic of TIs with low carrier density and small gap semiconducting behavior 42 , 52 .

Figure 9 Electrical resistivity temperature dependences measured for Bi 1.09 Gd 0.06 Sb 0.85 Te 3 (black and blue curves) and Bi 1.09 V 0.06 Sb 0.85 Te 3 (orange curve) at temperatures between 2 and 250 K.

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Observation of Restored Topological Surface States in Magnetically Doped Topological Insulator

“…To examine this suggestion, we compare some experimental results in similar systems. For example, Ce y Bi 2− y Te 3 and Gd z Bi 2− z Se 3 single crystals show antiferromagnetic ordering at y ≥ 0.08 and z ≥ 0.30, respectively, and their transport results reveal that the topologically non-trivial properties disappear in the antiferromagnetic states 20,21 . In the present work on Gd x Bi 2− x Te 3 , we observe no gap opening in the paramagnetic states ( x ≤ 0.10), but gap opening in the antiferromagnetic states ( x ≥ 0.15).…”

“…In theoretical expectation, AFM TI state is achieved for a particular combination of both TRS and translation symmetry breaking, and one of AFM TIs candidates is half-Heusler antiferromagnet GdBiPt 19 . On the other hand, there are some experimental observations of competing features between AFM order and topologically non-trivial phase 20,21 . To elucidate such ambiguity for the role of antiferromagnetism in TIs, the diverse reports on the TSS characteristics are needed as the AFM ordering evolves.…”

Roles of surface and bulk states in giant magnetoresistance and anomalous hall effect in antiferromagnetically ordered Bi1.9Dy0.1Te3topological insulators

“…4. 17,48,49 This suggests that the Ne ´el temperature (T N ) is around 10 K. Super exchange interaction between Dy 3+ ions via Te is the probable reason of antiferromagnetic coupling. 50 A similar behavior of magnetization with the applied magnetic field has been observed by many others in distinct magnetically ordered Bi 2 Te 3 systems.…”