Transport and magnetic properties of the diluted magnetic semiconductors Sb1.98–xV0.02Crx Te3 and Sb1.984–yV0.016Mny Te3

Drašar, Č.; Kašparová, J.; Losˇt'ák, P.; Shi, Xinying; Uher, Ctirad

doi:10.1002/pssb.200642486

Cited by 8 publications

(6 citation statements)

References 18 publications

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“…In dilute magnetic semiconductors, codoping is further predicted to lead to enhanced magnetic properties due to the interplay between the spin-polarized magnetic defects [32]. In fact, V-Cr codoping of Sb 2 Te 3 bulk crystals has been reported by Uher's group already in 2007 [33], and they observed an increased remanent magnetization for Sb 1.98−x V 0.02 Cr x Te 3 (0< x <0.022), while the transition temperatures were with ∼20 K comparable to only Cr-doped crystals. On the other hand, understanding and controlling the complex defect chemistry and formation of secondary phases is a great challenge in quaternary materials, in particular in thin films where grain boundaries are present.…”

Section: Introductionmentioning

confidence: 99%

Codoping ofSb2Te3thin films with V and Cr

Duffy

Figueroa

Laan

et al. 2017

Phys. Rev. Materials

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Magnetically doped topological insulators (TIs) are key to realizing the quantum anomalous Hall (QAH) effect, with the prospect of enabling dissipationless electronic devices in the future. Doping of the well-established three-dimensional TIs of the (Bi,Sb)2(Se,Te)3 family with the transition metals Cr and V is now an established approach for observing the QAH state at very low temperatures. While the magnetic transition temperatures of these materials is on the order of 10's of K, full quantization of the QAH state is achieved below ∼100 mK, governed by the size of the magnetic gap and thus the out-of-plane magnetic moment. In an attempt to raise the size of the magnetic moment and transition temperature, we carried out a structural and magnetic investigation of codoped (V,Cr):Sb2Te3 thin films. Starting from singly doped Cr:Sb2Te3 films, free of secondary phases and with a transition temperature of ∼72 K, we introduced increasing fractions of V and found a doubling of the transition temperature, while the magnetic moment decreases. In order to separate the properties and contributions of the two transition metals in the complex doping scenario independently, we employed spectroscopic x-ray techniques. Surprisingly, already small amounts of V lead to the formation of the secondary phase Cr2Te3. No V was detectable in the Sb2Te3 matrix. Instead, it acts as a surfactant and can be found in the near-surface layers at the end of the growth. Our study highlights the importance of x-ray-based studies for the doping of van der Waals systems, for which the optimization of magnetic moment or transition temperature alone is not necessarily a good strategy.

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Section: Introductionmentioning

confidence: 99%

Codoping ofSb2Te3thin films with V and Cr

Duffy

Figueroa

Laan

et al. 2017

Phys. Rev. Materials

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“…In an attempt to increase the useful QAHE temperature range, a number of more unconventional doping approaches have been successfully explored, such as co‐doping, modulation doping to separate the dopant from the charge‐carrying surface state layer, and doping with higher magnetic moment rare earth ions, to name a few. Note that co‐doping with different transition metals can also lead to undesired phase separations in this materials class, while modulation doping with Cr promises greater inherent benefits owing to the nature of the doping mechanism, which have, for example, led to the first successful observation of the axion insulator state .…”

Section: Introductionmentioning

confidence: 99%

Rare Earth Doping of Topological Insulators: A Brief Review of Thin Film and Heterostructure Systems

Hesjedal

2019

Physica Status Solidi (a)

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Magnetic topological insulators (MTIs) are a novel materials class in which a topologically nontrivial electronic band structure coexists with long-range ferromagnetic order. The ferromagnetic ground state can break time-reversal symmetry, opening a gap in the topological surface states whose size is dependent on the magnitude of the magnetic moment. Doping with rare earth ions is one way to introduce higher magnetic moments into a material, however, in Bi 2 Te 3 bulk crystals, the solubility limit is only a few percent. Using molecular beam epitaxy for the growth of doped (Sb,Bi) 2 (Se,Te) 3 TI thin films, high doping concentrations can be achieved while preserving their high crystalline quality. The growth, structural, electronic, and magnetic properties of Dy, Ho, and Gd doped TI thin films will be reviewed. Indeed, high magnetic moments can be introduced into the TIs, which are, however, not ferromagnetically ordered. By making use of interfacial effects, magnetic long-range order in Dy doped Bi 2 Te 3 , proximity-coupled to the MTI Cr:Sb 2 Te 3 , has been achieved. Clearly, engineered MTI heterostructures offer new possibilities that combine the advantageous properties of different layers, and thus provide an ideal materials platform enabling the observation new quantum effects at higher temperatures.

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“…We propose that the improvement in ferromagnetic homogeneity can be seen as deriving from the separately known properties of Cr‐ and V‐doped (Bi,Sb) 2 Te 3 as follows: The magnetic impurities of Cr‐doped (Bi,Sb) 2 Te 3 have larger atomic magnetic moment than those of V‐doped one . V‐doped (Bi,Sb) 2 Te 3 , on the other hand, has stronger perpendicular magnetic anisotropy as shown by the large coercivity.…”

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confidence: 99%

“…S z can be enhanced in Cr–V codoped films by a combination of a large magnetic moment and a strong perpendicular magnetic anisotropy. The larger S z in Cr–V codoped samples contributes to larger magnetic gap which can sustain the QAH effect at higher temperature and stabilize the ferromagnetic order…”

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confidence: 99%

Enhancing the Quantum Anomalous Hall Effect by Magnetic Codoping in a Topological Insulator

et al. 2017

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The quantum anomalous Hall (QAH) effect, which has been realized in magnetic topological insulators (TIs), is the key to applications of dissipationless quantum Hall edge states in electronic devices. However, investigations and utilizations of the QAH effect are limited by the ultralow temperatures needed to reach full quantization-usually below 100 mK in either Cr- or V-doped (Bi,Sb) Te of the two experimentally confirmed QAH materials. Here it is shown that by codoping Cr and V magnetic elements in (Bi,Sb) Te TI, the temperature of the QAH effect can be significantly increased such that full quantization is achieved at 300 mK, and zero-field Hall resistance of 0.97 h/e is observed at 1.5 K. A systematic transport study of the codoped (Bi,Sb) Te films with varied Cr/V ratios reveals that magnetic codoping improves the homogeneity of ferromagnetism and modulates the surface band structure. This work demonstrates magnetic codoping to be an effective strategy for achieving high-temperature QAH effect in TIs.

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Transport and magnetic properties of the diluted magnetic semiconductors Sb_1.98–xV_0.02Cr_x Te₃ and Sb_1.984–yV_0.016Mn_y Te₃

Cited by 8 publications

References 18 publications

Codoping ofSb2Te3thin films with V and Cr

Codoping ofSb2Te3thin films with V and Cr

Rare Earth Doping of Topological Insulators: A Brief Review of Thin Film and Heterostructure Systems

Enhancing the Quantum Anomalous Hall Effect by Magnetic Codoping in a Topological Insulator

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