Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures

Bhattacharjee, Nirjhar; Mahalingam, Krishnamurthy; Fedorko, A. S.; Will‐Cole, Alexandria; Ryu, Jaehyeon; Page, M. D.; McConney, Michael E.; Fang, Hui; Heiman, D.; Sun, Nian X.

doi:10.1021/acsaelm.2c00523

Cited by 5 publications

(8 citation statements)

References 44 publications

(79 reference statements)

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“…Measurement of m(H) Hysteresis Loops: Magnetization m(H) measurements were obtained using a Quantum Design MPMS XL-7 superconducting quantum interference device (SQUID) magnetometer. [42,43] Hysteresis loop m(H) measurements were carried out at various temperatures between 6 and 300 K. The ZFC m(T) measurements were obtained while increasing the temperature in an applied field of 50 Oe. Room temperature m(H) measurements were also taken using a vibrating sample magnetometer (VSM).…”

Section: Methodsmentioning

confidence: 99%

“…Without breaking the vacuum, the Bi 2 Te 3 /Py interface develops a topologically nontrivial AFM interfacial layer because of diffusion and reaction of Ni with Bi 2 Te 3 and forming NiBi 2 Te 4 . [42,43] In contrast, oxidizing the surface of the TI prevents reaction and diffusion of Ni or Fe from Py and does not allow forming a topological interfacial layer. To study the effect of surface oxidation of Bi 2 Te 3 on the interfacial diffusion and reactions in Bi 2 Te 3 /Py, room temperature m(H) measurements were performed on the samples of Bi 2 Te 3 /Py, Bi 2 Te 3 (oxidized)/Py, and Py (control) samples.…”

Section: Tio X Interlayer Effects On Diffusion In Ti/fm Heterostructuresmentioning

confidence: 99%

“…Ni and small amounts of Fe diffuse out from the Py and form interfacial compounds due to solid state reactions with Bi 2 Te 3 . [42,43] Looking at the saturation moment, it is clear that TiO x layers with thickness ≤1 nm cannot prevent interfacial diffusion of the magnetic species, which is aided by surface reaction with Bi 2 Te 3 . Note that the cited TiO x thickness, z TiOx is that of the Ti thin film deposited on a Si/SiO 2 substrate.…”

Section: Interface Engineering In Ti/fm Heterostructures Using Tio Xmentioning

confidence: 99%

“…Formation of an interfacial topological AFM layer generated by diffusion of Ni and solid-state reaction with Bi 2 Te 3 was shown previously. [42,43] The solid-state reaction was found to result in loss of magnetic moment and emergence of a large spontaneous exchange bias in Bi 2 Te 3 /Py heterostructures. The m(H) loop measurements at room temperature in Figure 4a show loss of magnetic moments in the Bi 2 Te 3 /TiO x /Py sample with the 1 nm thick TiO x , similar to the Bi 2 Te 3 /Py sample deposited with the same growth conditions.…”

Section: Tuning Of Topological Afm Interface With Tio X Barriermentioning

confidence: 99%

“…[42] AFM layers form at the interface in Bi 2 Te 3 /Py, and Bi 2 Te 3 /TiO x /Py samples as a result of interdiffusion and solid state reaction with the TI surface states. [42,43] In order to understand the effect of interfacial magnetic properties of the Bi 2 Te 3 /TiO x /NZFO heterostructure samples, m(H) loop measurements were performed at 300 and 6 K similar those shown in Sections 2.1.2 and 2.2. The m(H) loop at 300 K for the z TiOx = 1 nm Bi 2 Te 3 /TiO x /NZFO sample was well centered.…”

Section: Interfacial Afm Phase In Bi 2 Te 3 /Tio X /Nzfo Heterostruct...mentioning

confidence: 99%

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Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator

Bhattacharjee

Mahalingam

Will‐Cole

et al. 2022

Adv Materials Inter

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Realization of the quantum anomalous Hall (QAH) effect has been demonstrated in several magnetic topological insulators (MTIs). MTIs can be synthesized by doping magnetic elements into topological insulators (TIs) [1][2][3][4][5][6][7][8][9] or growth of intrinsic MTI compounds. [10][11][12][13][14][15][16][17][18][19] However, these MTI materials require temperatures much lower than their magnetic T c to achieve quantization in the Hall effect. This deficiency has been attributed to inhomogeneity in magnetic doping which causes localized variation in surface state exchange gaps. Magnetism can also be induced in the surface of TI thin films via proximity exchange effect. This proximity induced magnetization (PIM) is envisioned by coupling TIs with a magnetic insulator (MI). PIM in TIs have been experimentally confirmed in heterostructures of TIs with magnetic insulators (MIs) such as rare earth garnets and EuS, [20][21][22][23][24][25][26][27][28] MTIs, [29,30] and telluride van der Waals (vdW) magnets. [31] However, recent studies have pointed out the complexities in measuring proximity exchange in these systems, [31] which can be affected by a number of problems such as diffusion at the interface and band bending. Thus, providing a barrier for diffusion while permitting magnetic exchange in TI/MI heterostructures will be necessary for devices, and it is shown here that a TiO x interface barrier achieves this goal. Only a single study by Watanabe et al. [31] has shown PIM and QAH in a TI/MI/TI thin film sandwich structure of (Zn,Cr)Te/(Bi,Sb) 2 Te 3 /(Zn,Cr)Te. However, even in this material system, the QAH effect was seen at extremely low temperature of 0.03 K. This low temperature is possibly due to: (1) High-quality MIs which were grown on TI thin films have very low Curie temperature, T c , such as (Zn,Cr) Te with T c < 40 K [31] and EuS with T c of ≈17 K. [25] (2) Even with 20-25% of the magnetic species, Cr in (Zn,Cr)Te, finite localized nonmagnetic nanoregions may exist in the samples.MIs such as rare-earth garnets and ferrites are excellent materials that are magnetically ordered well above room-temperature, making them ideal candidates for QAH materials coupled with TIs. However, growth of MIs on top of TIs using Combining topological insulators (TIs) and magnetic materials in heterostructures is crucial for advancing spin-based electronics. Magnetic insulators (MIs) can be deposited on TIs using the spin-spray process, which is a unique nonvacuum, low-temperature growth process. TIs have highly reactive surfaces that oxidize upon exposure to atmosphere, making it challenging to grow spinspray ferrites on TIs. In this work, it is demonstrated that a thin titanium capping layer on TI, followed by oxidation in atmosphere to produce a thin TiO x interfacial layer, protects the TI surface, without significantly compromising spin transport from the magnetic material across the TiO x to the TI surface states. First, it is demonstrated that in Bi 2 Te 3 /TiO x /Ni 80 Fe 20 heterostructures, TiO x provides an e...

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Section: Methodsmentioning

confidence: 99%

Section: Tio X Interlayer Effects On Diffusion In Ti/fm Heterostructuresmentioning

confidence: 99%

Section: Interface Engineering In Ti/fm Heterostructures Using Tio Xmentioning

confidence: 99%

Section: Tuning Of Topological Afm Interface With Tio X Barriermentioning

confidence: 99%

Section: Interfacial Afm Phase In Bi 2 Te 3 /Tio X /Nzfo Heterostruct...mentioning

confidence: 99%

See 3 more Smart Citations

Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator

Bhattacharjee

Mahalingam

Will‐Cole

et al. 2022

Adv Materials Inter

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Recent progress in strong spin-orbit coupling van der Waals materials and their heterostructures for spintronic applications

Shi,

Wang,

Zhao

et al. 2023

Materials Today Electronics

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Comparing spin injection in Fe75Co25/Bi2Te3 at GHz and optical excitations

Sharma

Nepal

et al. 2023

Applied Physics Letters

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Spin-to-charge conversion (S2CC) processes in thin-film heterostructures have attracted much attention in recent years. Here, we describe the S2CC in a 3D topological insulator Bi2Te3 interfaced with an epitaxial film of Fe75Co25. The quantification of spin-to-charge conversion is made with two complementary techniques: ferromagnetic resonance based inverse spin Hall effect (ISHE) at GHz frequencies and femtosecond light-pulse induced emission of terahertz (THz) radiation. The role of spin rectification due to extrinsic effects like anisotropic magnetoresistance (AMR) and planar Hall effects (PHE) is pronounced at the GHz timescale, whereas the THz measurements do not show any detectible signal, which could be attributed to AMR or PHE. This result may be due to (i) homodyne rectification at GHz, which is absent in THz measurements and (ii) laser-induced thermal spin current generation and magnetic dipole radiation in THz measurements, which is completely absent in GHz range. The converted charge current has been analyzed using the spin diffusion model for the ISHE. We note that regardless of the differences in timescales, the spin diffusion length in the two cases is comparable. Our results aid in understanding the role of spin pumping timescales in the generation of ISHE signals.

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Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures

Cited by 5 publications

References 44 publications

Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator

Interface Engineering Enabled Low Temperature Growth of Magnetic Insulator on Topological Insulator

Recent progress in strong spin-orbit coupling van der Waals materials and their heterostructures for spintronic applications

Comparing spin injection in Fe75Co25/Bi2Te3 at GHz and optical excitations

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