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11 pages, 2026 KiB

Open AccessArticle

Characterization of Mn₅Ge₃ Contacts on a Shallow Ge/SiGe Heterostructure

by Troy A. Hutchins-Delgado, Sadhvikas J. Addamane, Ping Lu and Tzu-Ming Lu

Nanomaterials 2024, 14(6), 539; https://doi.org/10.3390/nano14060539 - 19 Mar 2024

Viewed by 678

Abstract

M n_{5} G e_{3}

is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of

M n_{5} G e_{3}

-based contacts on a Ge/SiGe [...] Read more.

M n_{5} G e_{3}

is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of

M n_{5} G e_{3}

-based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of

M n_{5} G e_{3}

-based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct

M n_{5} G e_{3}

-based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that

M n_{5} G e_{3}

-based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of

0.10

e V

(extracted from a

M n_{5} G e_{3}

/n-Ge analogue) and a contact resistance in the order of 1

k

Ω

. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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12 pages, 12845 KiB

Open AccessFeature PaperArticle

Colossal Magnetoresistance in Layered Diluted Magnetic Semiconductor Rb(Zn,Li,Mn)₄As₃ Single Crystals

by Yi Peng, Luchuan Shi, Guoqiang Zhao, Jun Zhang, Jianfa Zhao, Xiancheng Wang, Zheng Deng and Changqing Jin

Nanomaterials 2024, 14(3), 263; https://doi.org/10.3390/nano14030263 - 25 Jan 2024

Viewed by 698

Abstract

Diluted magnetic semiconductors (DMSs) with tunable ferromagnetism are among the most promising materials for fabricating spintronic devices. Some DMS systems have sizeable magnetoresistances that can further extend their applications. Here, we report a new DMS Rb(Zn_1−x−yLi_yMn [...] Read more.

Diluted magnetic semiconductors (DMSs) with tunable ferromagnetism are among the most promising materials for fabricating spintronic devices. Some DMS systems have sizeable magnetoresistances that can further extend their applications. Here, we report a new DMS Rb(Zn_1−x−yLi_yMn_x)₄As₃ with a quasi-two-dimensional structure showing sizeable anisotropies in its ferromagnetism and transverse magnetoresistance (MR). With proper charge and spin doping, single crystals of the DMS display Curie temperatures up to 24 K. Analysis of the critical behavior via Arrott plots confirms the long-range ferromagnetic ordering in the Rb(Zn_1−x−yLi_yMn_x)₄As₃ single crystals. We observed remarkable intrinsic MR effects in the single crystals (i.e., a positive MR of 85% at 0.4 T and a colossal negative MR of −93% at 7 T). Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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11 pages, 2249 KiB

Open AccessArticle

The Influence of Capping Layers on Tunneling Magnetoresistance and Microstructure in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions upon Annealing

by Geunwoo Kim, Soogil Lee, Sanghwa Lee, Byonggwon Song, Byung-Kyu Lee, Duhyun Lee, Jin Seo Lee, Min Hyeok Lee, Young Keun Kim and Byong-Guk Park

Nanomaterials 2023, 13(18), 2591; https://doi.org/10.3390/nano13182591 - 19 Sep 2023

Viewed by 1234

Abstract

This study investigates the effects of annealing on the tunnel magnetoresistance (TMR) ratio in CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with different capping layers and correlates them with microstructural changes. It is found that the capping layer plays an important role in determining the [...] Read more.

This study investigates the effects of annealing on the tunnel magnetoresistance (TMR) ratio in CoFeB/MgO/CoFeB-based magnetic tunnel junctions (MTJs) with different capping layers and correlates them with microstructural changes. It is found that the capping layer plays an important role in determining the maximum TMR ratio and the corresponding annealing temperature (T_ann). For a Pt capping layer, the TMR reaches ~95% at a T_ann of 350 °C, then decreases upon a further increase in T_ann. A microstructural analysis reveals that the low TMR is due to severe intermixing in the Pt/CoFeB layers. On the other hand, when introducing a Ta capping layer with suppressed diffusion into the CoFeB layer, the TMR continues to increase with T_ann up to 400 °C, reaching ~250%. Our findings indicate that the proper selection of a capping layer can increase the annealing temperature of MTJs so that it becomes compatible with the complementary metal-oxide-semiconductor backend process. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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12 pages, 2688 KiB

Open AccessArticle

Circular Photogalvanic Current in Ni-Doped Cd₃As₂ Films Epitaxied on GaAs(111)B Substrate

by Gaoming Liang, Guihao Zhai, Jialin Ma, Hailong Wang, Jianhua Zhao, Xiaoguang Wu and Xinhui Zhang

Nanomaterials 2023, 13(13), 1979; https://doi.org/10.3390/nano13131979 - 29 Jun 2023

Viewed by 1049

Abstract

Magnetic element doped Cd₃As₂ Dirac semimetal has attracted great attention for revealing the novel quantum phenomena and infrared opto-electronic applications. In this work, the circular photogalvanic effect (CPGE) was investigated at various temperatures for the Ni-doped Cd₃As₂ [...] Read more.

Magnetic element doped Cd₃As₂ Dirac semimetal has attracted great attention for revealing the novel quantum phenomena and infrared opto-electronic applications. In this work, the circular photogalvanic effect (CPGE) was investigated at various temperatures for the Ni-doped Cd₃As₂ films which were grown on GaAs(111)B substrate by molecular beam epitaxy. The CPGE current generation was found to originate from the structural symmetry breaking induced by the lattice strain and magnetic doping in the Ni-doped Cd₃As₂ films, similar to that in the undoped ones. However, the CPGE current generated in the Ni-doped Cd₃As₂ films was approximately two orders of magnitude smaller than that in the undoped one under the same experimental conditions and exhibited a complex temperature variation. While the CPGE current in the undoped film showed a general increase with rising temperature. The greatly reduced CPGE current generation efficiency and its complex variation with temperature in the Ni-doped Cd₃As₂ films was discussed to result from the efficient capture of photo-generated carriers by the deep-level magnetic impurity bands and enhanced momentum relaxation caused by additional strong impurity scattering when magnetic dopants were introduced. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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12 pages, 11855 KiB

Open AccessArticle

Mn-X (X = F, Cl, Br, I) Co-Doped GeSe Monolayers: Stabilities and Electronic, Spintronic and Optical Properties

by Wenjie He, Xi Zhang, Dan Gong, Ya Nie and Gang Xiang

Nanomaterials 2023, 13(12), 1862; https://doi.org/10.3390/nano13121862 - 15 Jun 2023

Cited by 1 | Viewed by 896

Abstract

GeSe monolayer (ML) has recently attracted much interest due to its unique structure and excellent physical properties that can be effectively tuned through single doping of various elements. However, the co-doping effects on GeSe ML are rarely studied. In this study, the structures [...] Read more.

GeSe monolayer (ML) has recently attracted much interest due to its unique structure and excellent physical properties that can be effectively tuned through single doping of various elements. However, the co-doping effects on GeSe ML are rarely studied. In this study, the structures and physical properties of Mn-X (X = F, Cl, Br, I) co-doped GeSe MLs are investigated by using first-principle calculations. The formation energy and phonon disspersion analyses reveal the stability of Mn-Cl and Mn-Br co-doped GeSe MLs and instability of Mn-F and Mn-I co-doped GeSe MLs. The stable Mn-X (X = Cl, Br) co-doped GeSe MLs exhibit complex bonding structures with respect to Mn-doped GeSe ML. More importantly, Mn-Cl and Mn-Br co-doping can not only tune magnetic properties, but also change the electronic properties of GeSe MLs, which makes Mn-X co-doped GeSe MLs indirect band semiconductors with anisotropic large carrier mobility and asymmetric spin-dependent band structures. Furthermore, Mn-X (X = Cl, Br) co-doped GeSe MLs show weakened in-plane optical absorption and reflection in the visible band. Our results may be useful for electronic, spintronic and optical applications based on Mn-X co-doped GeSe MLs. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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9 pages, 7365 KiB

Open AccessArticle

Controllable Synthesis and Charge Density Wave Phase Transitions of Two-Dimensional 1T-TaS₂ Crystals

by Xiaoguang Pan, Tianwen Yang, Hangxin Bai, Jiangbo Peng, Lujie Li, Fangli Jing, Hailong Qiu, Hongjun Liu and Zhanggui Hu

Nanomaterials 2023, 13(11), 1806; https://doi.org/10.3390/nano13111806 - 05 Jun 2023

Cited by 1 | Viewed by 1692

Abstract

1T-TaS₂ has attracted much attention recently due to its abundant charge density wave phases. In this work, high-quality two-dimensional 1T-TaS₂ crystals were successfully synthesized by a chemical vapor deposition method with controllable layer numbers, confirmed by the structural characterization. Based on [...] Read more.

1T-TaS₂ has attracted much attention recently due to its abundant charge density wave phases. In this work, high-quality two-dimensional 1T-TaS₂ crystals were successfully synthesized by a chemical vapor deposition method with controllable layer numbers, confirmed by the structural characterization. Based on the as-grown samples, their thickness-dependency nearly commensurate charge density wave/commensurate charge density wave phase transitions was revealed by the combination of the temperature-dependent resistance measurements and Raman spectra. The phase transition temperature increased with increasing thickness, but no apparent phase transition was found on the 2~3 nm thick crystals from temperature-dependent Raman spectra. The transition hysteresis loops due to temperature-dependent resistance changes of 1T-TaS₂ can be used for memory devices and oscillators, making 1T-TaS₂ a promising material for various electronic applications. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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14 pages, 6054 KiB

Open AccessArticle

Size-Dependent Superconducting Properties of In Nanowire Arrays

by Alexey A. Noyan, Yevgeniy A. Ovchenkov, Valery V. Ryazanov, Igor A. Golovchanskiy, Vasily S. Stolyarov, Eduard E. Levin and Kirill S. Napolskii

Nanomaterials 2022, 12(22), 4095; https://doi.org/10.3390/nano12224095 - 21 Nov 2022

Viewed by 1629

Abstract

Arrays of superconducting nanowires may be useful as elements of novel nanoelectronic devices. The superconducting properties of nanowires differ significantly from the properties of bulk structures. For instance, different vortex configurations of the magnetic field have previously been predicted for nanowires with different [...] Read more.

Arrays of superconducting nanowires may be useful as elements of novel nanoelectronic devices. The superconducting properties of nanowires differ significantly from the properties of bulk structures. For instance, different vortex configurations of the magnetic field have previously been predicted for nanowires with different diameters. In the present study, arrays of parallel superconducting In nanowires with the diameters of 45 nm, 200 nm, and 550 nm—the same order of magnitude as coherence length ξ—were fabricated by templated electrodeposition. Values of magnetic moment M of the samples were measured as a function of magnetic field H and temperature T in axial and transverse fields. M(H) curves for the arrays of nanowires with 45 nm and 200 nm diameters are reversible, whereas magnetization curves for the array of nanowires with 550 nm diameter have several feature points and show a significant difference between increasing and decreasing field branches. Critical fields increase with a decrease in diameter, and the thinnest nanowires exceed bulk critical fields by 20 times. The qualitative change indicates that magnetic field configurations are different in the nanowires with different diameters. Variation of M(H) slope in small fields, heat capacity, and the magnetic field penetration depth with the temperature were measured. Superconductivity in In nanowires is proven to exist above the bulk critical temperature. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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8 pages, 1348 KiB

Open AccessEditor’s ChoiceArticle

Significant Modulation of Vortex Resonance Spectra in a Square-Shape Ferromagnetic Dot

by Shaojie Hu, Xiaomin Cui, Kang Wang, Satoshi Yakata and Takashi Kimura

Nanomaterials 2022, 12(13), 2295; https://doi.org/10.3390/nano12132295 - 04 Jul 2022

Viewed by 1375

Abstract

The resonance property of a magnetic vortex contained within a micron-sized square Py dot was detected using an amplitude-modulated magnetic field excitation technique. We found a significant modulation of the resonant spectra as the external magnetic field changes. The Lorentzian-like spectrum changes from [...] Read more.

The resonance property of a magnetic vortex contained within a micron-sized square Py dot was detected using an amplitude-modulated magnetic field excitation technique. We found a significant modulation of the resonant spectra as the external magnetic field changes. The Lorentzian-like spectrum changes from a peak to a dip via a transition of anti-Lorentzian-like spectra. By conducting the micromagnetic simulations, we confirmed that the transition behavior results from the unusual resistance change depending on the vortex core center position. Additionally, the power dependence of the anti-Lorentzian-like spectra revealed a fairly persistent coexistence of peak and dip. Thus, the tunable spectra suggest one way to develop an integratable radiofrequency microcircuits. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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Review

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23 pages, 18868 KiB

Open AccessReview

Strain Engineering of Intrinsic Ferromagnetism in 2D van der Waals Materials

by Hongtao Ren and Gang Xiang

Nanomaterials 2023, 13(16), 2378; https://doi.org/10.3390/nano13162378 - 19 Aug 2023

Cited by 2 | Viewed by 1640

Abstract

Since the discovery of the low-temperature, long-range ferromagnetic order in monolayers Cr₂Ge₂Te₆ and CrI₃, many efforts have been made to achieve a room temperature (RT) ferromagnet. The outstanding deformation ability of two-dimensional (2D) materials provides an [...] Read more.

Since the discovery of the low-temperature, long-range ferromagnetic order in monolayers Cr₂Ge₂Te₆ and CrI₃, many efforts have been made to achieve a room temperature (RT) ferromagnet. The outstanding deformation ability of two-dimensional (2D) materials provides an exciting way to mediate their intrinsic ferromagnetism (FM) with strain engineering. Here, we summarize the recent progress of strain engineering of intrinsic FM in 2D van der Waals materials. First, we introduce how to explain the strain-mediated intrinsic FM on Cr-based and Fe-based 2D van der Waals materials through ab initio Density functional theory (DFT), and how to calculate magnetic anisotropy energy (MAE) and Curie temperature (T_C) from the interlayer exchange coupling J. Subsequently, we focus on numerous attempts to apply strain to 2D materials in experiments, including wrinkle-induced strain, flexible substrate bending or stretching, lattice mismatch, electrostatic force and field-cooling. Last, we emphasize that this field is still in early stages, and there are many challenges that need to be overcome. More importantly, strengthening the guideline of strain-mediated FM in 2D van der Waals materials will promote the development of spintronics and straintronics. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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19 pages, 1918 KiB

Open AccessReview

Recent Advances in the Spintronic Application of Carbon-Based Nanomaterials

by Shweta Pawar, Hamootal Duadi and Dror Fixler

Nanomaterials 2023, 13(3), 598; https://doi.org/10.3390/nano13030598 - 02 Feb 2023

Cited by 6 | Viewed by 2743

Abstract

The term “carbon-based spintronics” mostly refers to the spin applications in carbon materials such as graphene, fullerene, carbon nitride, and carbon nanotubes. Carbon-based spintronics and their devices have undergone extraordinary development recently. The causes of spin relaxation and the characteristics of spin transport [...] Read more.

The term “carbon-based spintronics” mostly refers to the spin applications in carbon materials such as graphene, fullerene, carbon nitride, and carbon nanotubes. Carbon-based spintronics and their devices have undergone extraordinary development recently. The causes of spin relaxation and the characteristics of spin transport in carbon materials, namely for graphene and carbon nanotubes, have been the subject of several theoretical and experimental studies. This article gives a summary of the present state of research and technological advancements for spintronic applications in carbon-based materials. We discuss the benefits and challenges of several spin-enabled, carbon-based applications. The advantages include the fact that they are significantly less volatile than charge-based electronics. The challenge is in being able to scale up to mass production. Full article

(This article belongs to the Special Issue Advanced Spintronic and Electronic Nanomaterials)

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