Exchange Bias in Magnetic Topological Insulator Superlattices

Liu, Jieyi; Singh, Angadjit; Liu, Yu Yang Fredrik; Ionescu, Adrian M.; Kuerbanjiang, Balati; Barnes, C. H. W.; Hesjedal, T.

doi:10.1021/acs.nanolett.0c01666

Cited by 11 publications

(14 citation statements)

References 42 publications

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“…Figure 2d plots the derivative, d m /d T of the ZFC m ( T ), showing a sharp peak at 63 K, which is the Neél transition temperature of the AFM phase. [ 42,43 ] This Neél temperature of the Ni‐Bi 2 Te 3 AFM phase is higher than the transition temperatures of MTIs reported in the literature. [ 54 ]…”

Section: Resultsmentioning

confidence: 71%

“…This EB shift and μ 0 H c enhancement is a characteristic of a large exchange interaction in the FM/ AFM interface. [40][41][42][43] A high energy of the exchange interaction between the FM and AFM layers not only shifts the loop m(H) loop along the axis of the H-field (exchange bias), but often also leads to an increase in coercive field. [40,41] This possibly happens due to the pinning of domains in a magnetic frustrated interface.…”

Section: Exchange Bias Due To Fm/afm Interactionmentioning

confidence: 99%

“…Measurements of the magnetic hysteresis loops show the appearance of a large spontaneous exchange bias (EB), signaling an AFM phase in proximity to the FM layer of Py having substantial exchange interaction between the AFM-FM layers. [38][39][40][41][42][43][44][45] The location of the AFM order in the interface of the Bi 2 Te 3 /Py heterostructure was confirmed using polarized neutron reflectometry (PNR) experiments. In addition, using selected-area electron diffraction (SAED) we observed new diffraction peaks emerging in the AFM Ni-Bi 2 Te 3 layer, in addition to the Bi 2 Te 3 peaks signaling the appearance of new planes along the crystalline c-axis.…”

Section: Introductionmentioning

confidence: 99%

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Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS‐Compatible Sputtering Technique

et al. 2022

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Breaking time‐reversal symmetry by introducing magnetic order, thereby opening a gap in the topological surface state bands, is essential for realizing useful topological properties such as the quantum anomalous Hall and axion insulator states. In this work, a novel topological antiferromagnetic (AFM) phase is created at the interface of a sputtered, c‐axis‐oriented, topological insulator/ferromagnet heterostructure—Bi2Te3/Ni80Fe20 because of diffusion of Ni in Bi2Te3 (Ni‐Bi2Te3). The AFM property of the Ni‐Bi2Te3 interfacial layer is established by observation of spontaneous exchange bias in the magnetic hysteresis loop and compensated moments in the depth profile of the magnetization using polarized neutron reflectometry. Analysis of the structural and chemical properties of the Ni‐Bi2Te3 layer is carried out using selected‐area electron diffraction, electron energy loss spectroscopy, and X‐ray photoelectron spectroscopy. These studies, in parallel with first‐principles calculations, indicate a solid‐state chemical reaction that leads to the formation of Ni−Te bonds and the presence of topological antiferromagnetic (AFM) compound NiBi2Te4 in the Ni‐Bi2Te3 interface layer. The Neél temperature of the Ni‐Bi2Te3 layer is ≈63 K, which is higher than that of typical magnetic topological insulators (MTIs). The presented results provide a pathway toward industrial complementary metal−oxide−semiconductor (CMOS)‐process‐compatible sputtered‐MTI heterostructures, leading to novel materials for topological quantum devices.

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Section: Resultsmentioning

confidence: 71%

Section: Exchange Bias Due To Fm/afm Interactionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS‐Compatible Sputtering Technique

et al. 2022

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“…f) Temperature-dependent magnetization of the [CST/DBT] 10 superlattice and CST single-layer film. Adapted under the terms of the CC-BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0) [210]. Copyright 2020, The Authors, published by American Chemical Society.…”

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confidence: 99%

Magnetic Topological Insulator Heterostructures: A Review

Liu

Hesjedal

2021

Advanced Materials

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Chern number corresponds to the occupancy of discrete Landau levels, which can be varied by tuning the Fermi energy via a gate voltage. It further corresponds to the number of dissipationless conduction channels in the gapless edge state of the quantum Hall insulator that is insulating in the bulk in high magnetic fields.After observing the quantum version of the Hall effect, the natural question to ask is if there is also a quantized version of the anomalous Hall effect (AHE), commonly observed in ferromagnets. This quantum anomalous Hall effect (QAHE) would then be observable in the absence of external fields. The QAHE was initially proposed to arise in 2D honeycomb or kagome lattices, such as monolayer graphene, that host a non-zero out-of-plane magnetic flux density, but zero net flux in each unit cell. [8,9] Later, it was also proposed that the QAHE may be found in Hg 1−y Mn y Te quantum wells without an external magnetic field, in which the effect arises purely due to the spin polarization of the Mn atoms. [10] However, the experimental realization of the QAHE was not reported until 2013, when transport in 3D topological insulators (TIs) doped with magnetic impurities was studied. TIs refer to a class of materials that is insulating in the bulk, but which possess topologically protected conducting surface states. Right from the start, the field was (see refs. [6,11-17]), and continues to be (see refs. [18-20]), to a large degree driven by theory. Common examples of 3D TIs are rhombohedral Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 . [15] The surface state of a TI consists of two linearly dispersing states connecting the bulk conduction and valence bands. The two states cross at one point in reciprocal space, the Dirac point (Figure 1a). The charge carriers in this band structure are massless fermions, which are described by the relativistic Dirac equation. [15] Due to the strong spin-orbit coupling (SOC) in these materials, surface electron spins are locked to their momentum, forming dissipationless, counter-propagating conduction channels in the surface state.By introducing magnetism to a TI, either by impurity doping with magnetic elements, by proximity coupling to a magnetic insulators (MIs), or other magnetic layers, time-reversal symmetry (TRS) can be broken. TRS breaking can induce a bandgap in the surface states, leading to the realization of the QAHE which is characterized by 1D chiral edge conduction in zerofield at remanence, as shown in Figure 1. The Chern number, here being +1 or -1, corresponds to the direction of the spinmomentum locked edge current that can be flipped by a (small) external field. Using first-principles calculations, Sb 2 Te 3 , Bi 2 Te 3 , Topological insulators (TIs) provide intriguing prospects for the future of spintronics due to their large spin-orbit coupling and dissipationless, counterpropagating conduction channels in the surface state. The combination of topological properties and magnetic order can lead to new quantum states including the quantum anomalous Hall effect th...

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“…There are two main types of exchange bias effect research, the horizontal exchange bias effect (EB) and the vertical magnetization shift (VMS). EB is the offset of the hysteresis loop along the field axis, which is observed and studied in many materials [5][6][7][8][9][10][11][12]; VMS is the offset of the hysteresis loop along the magnetization axis, which is only found in a small number of systems [13][14][15][16][17][18]. M E denotes the shift of the center of gravity of the hysteresis loop along the magnetization axis.…”

Section: Introductionmentioning

confidence: 99%

Giant Vertical Magnetization Shift Caused by Field-Induced Ferromagnetic Spin Reconfiguration in Ni50Mn36Ga14 Alloy

et al. 2020

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Vertical magnetization shift (VMS) is a special type of exchange bias effect that may lead to a revolution in future ultrahigh-density magnetic recording technology. However, there are very few reports focusing on the performance of VMS due to the unclear mechanism. In this paper, a giant vertical magnetization shift (ME) of 6.34 emu/g is reported in the Ni50Mn36Ga14 alloy. The VMS can be attributed to small ferromagnetic ordered regions formed by spin reconfiguration after field cooling, which are embedded in an antiferromagnetic matrix. The strong cooling-field dependence, temperature dependence, and training effect all corroborate the presence of spin reconfiguration and its role in the VMS. This work can enrich VMS research and increase its potential in practical applications as well.

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Exchange Bias in Magnetic Topological Insulator Superlattices

Cited by 11 publications

References 42 publications

Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS‐Compatible Sputtering Technique

Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS‐Compatible Sputtering Technique

Magnetic Topological Insulator Heterostructures: A Review

Giant Vertical Magnetization Shift Caused by Field-Induced Ferromagnetic Spin Reconfiguration in Ni50Mn36Ga14 Alloy

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