1
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Backes D, Fujita R, Veiga LSI, Mayoh DA, Wood GDA, Dhesi SS, Balakrishnan G, van der Laan G, Hesjedal T. Valence-state mixing and reduced magnetic moment inFe3-δGeTe2single crystals with varying Fe content probed by x-ray spectroscopy. NANOTECHNOLOGY 2024; 35:395709. [PMID: 38959868 DOI: 10.1088/1361-6528/ad5e87] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 07/03/2024] [Indexed: 07/05/2024]
Abstract
We present a spectroscopic study of the magnetic properties ofFe3-δGeTe2single crystals with varying Fe content, achieved by tuning the stoichiometry of the crystals. We carried out x-ray absorption spectroscopy and analyzed the x-ray circular magnetic dichroism spectra using the sum rules, to determine the orbital and spin magnetic moments of the materials. We find a clear reduction of the spin and orbital magnetic moment with increasing Fe deficiency. Magnetic susceptibility measurements show that the reduction in magnetization is accompanied by a reduced Curie temperature. Multiplet calculations reveal that the Fe2+state increasingly mixes with a higher valence state when the Fe deficiency is increased. This effect is correlated with the weakening of the magnetic moment. As single crystals are the base material for exfoliation processes, our results are relevant for the assembly of 2D magnetic heterostructures.
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Affiliation(s)
- D Backes
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - R Fujita
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - L S I Veiga
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - D A Mayoh
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G D A Wood
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - S S Dhesi
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - G Balakrishnan
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - T Hesjedal
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
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2
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Lim H, Ahn HB, Lee C. Magnetic properties of ferromagnetic nanoparticles of Fe xGeTe 2( x= 3, 5) directly exfoliated and dispersed in pure water. NANOTECHNOLOGY 2024; 35:395604. [PMID: 38959866 DOI: 10.1088/1361-6528/ad5e8a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 07/03/2024] [Indexed: 07/05/2024]
Abstract
FexGeTe2(x= 3, 5) are two-dimensional ferromagnetic (FM) materials that have gained significant attention from researchers due to their relatively high Curie temperature and tunability. However, the methods for preparing FM nanoparticles (FNPs) and large-area FexGeTe2films are still in the early stages. Here, we studied the magnetic properties of FexGeTe2FNPs exfoliated via wet exfoliation in pure water. The coercive field of Fe3GeTe2FNPs increases significantly, up to 60 times, while that of Fe5GeTe2only slightly increases from that of bulk crystals. Further investigation related to the dimension of nanoparticles and the Henkel plot analysis reveals that the variation in their coercive field stems from the material's thickness-dependent coercive field and the type of term that governs the interaction between single-domain nanoparticles. Our work demonstrates a facile method for preparing FNPs using van der Waals FM materials and tuning their magnetic properties.
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Affiliation(s)
- Hyunjong Lim
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hyo-Bin Ahn
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Changgu Lee
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
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3
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Gu K, Zhang X, Liu X, Guo X, Wu Z, Wang S, Song Q, Wang W, Wei L, Liu P, Ma J, Xu Y, Niu W, Pu Y. Exchange Bias Modulated by Antiferromagnetic Spin-Flop Transition in 2D Van der Waals Heterostructures. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2307034. [PMID: 38353386 PMCID: PMC11077673 DOI: 10.1002/advs.202307034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 01/29/2024] [Indexed: 05/09/2024]
Abstract
Exchange bias is extensively studied and widely utilized in spintronic devices, such as spin valves and magnetic tunnel junctions. 2D van der Waals (vdW) magnets, with high-quality interfaces in heterostructures, provide an excellent platform for investigating the exchange bias effect. To date, intrinsic modulation of exchange bias, for instance, via precise manipulation of the magnetic phases of the antiferromagnetic layer, is yet to be fully reached, owing partly to the large exchange fields of traditional bulk antiferromagnets. Herein, motivated by the low-field spin-flop transition of a 2D antiferromagnet, CrPS4, exchange bias is explored by modulating the antiferromagnetic spin-flop phase transition in all-vdW magnetic heterostructures. The results demonstrate that undergoing the spin-flop transition during the field cooling process, the A-type antiferromagnetic ground state of CrPS4 turns into a canted antiferromagnetic one, therefore, it reduces the interfacial magnetic coupling and suppresses the exchange bias. Via conducting different cooling fields, one can select the exchange bias effect switching among the "ON", "depressed", and "OFF" states determined by the spin flop of CrPS4. This work provides an approach to intrinsically modulate the exchange bias in all-vdW heterostructures and paves new avenues to design and manipulate 2D spintronic devices.
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Affiliation(s)
- Kai Gu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Xiaoqian Zhang
- Key Laboratory of Quantum Materials and Devices of Ministry of EducationSchool of PhysicsSoutheast UniversityNanjing211189China
- International Quantum AcademyShenzhen518048China
| | - Xiangjie Liu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Xinlei Guo
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Zhenqi Wu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Shuo Wang
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Qinxin Song
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Wei Wang
- Key Laboratory of Flexible Electronics & Institute of Advanced MaterialsJiangsu National Synergetic Innovation Center for Advanced MaterialsNanjing Tech UniversityNanjing211816China
| | - Lujun Wei
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Ping Liu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
| | - Jingrui Ma
- Key Laboratory of Energy Conversion and Storage TechnologiesSouthern University of Science and TechnologyShenzhen518055China
| | - Yongbing Xu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
- School of Electronic Science and EngineeringNanjing UniversityNanjing210023China
| | - Wei Niu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
- Key Laboratory of Energy Conversion and Storage TechnologiesSouthern University of Science and TechnologyShenzhen518055China
| | - Yong Pu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of ScienceNanjing University of Posts and TelecommunicationsNanjing210023China
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4
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Miao W, Zhen W, Tan C, Wang J, Nie Y, Wang H, Wang L, Niu Q, Tian M. Nonreciprocal Antisymmetric Magnetoresistance and Unconventional Hall Effect in a Two-Dimensional Ferromagnet. ACS NANO 2023; 17:25449-25458. [PMID: 38051216 DOI: 10.1021/acsnano.3c08954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Two-dimensional (2D) ferromagnets with high Curie temperatures provide a rich platform for exploring the exotic phenomena of 2D magnetism and the potential of spintronic devices. As a prototypical 2D ferromagnet, Fe5-xGeTe2 has recently been reported to possess a high Curie temperature with Tc ∼ 310 K, making it a promising candidate for advancing 2D nanoelectromechanical systems. However, due to its intricate magnetic ground state and magnetic domains, a thorough study of the transport behavior related to its lattice and domain structures is still lacking. Here, we report a nonreciprocal antisymmetric magnetoresistance in Fe5-xGeTe2 nanoflakes observed under an external magnetic field between 85-120 K. Through a detailed examination of its temperature, field orientation, and sample thickness dependence, we trace its origin to an additional electric field induced by the domain structure. This differs from the previously reported antisymmetric magnetoresistance due to thickness inhomogeneity. Notably, at lower temperatures, we observed an unconventional Hall effect (UHE), which can be attributed to the Dzyaloshinskii-Moriya interaction (DMI) resulting from the non-coplanar magnetic moment structure. The pronounced influence of sample thickness on magneto-transport properties underscores the competition between magnetic anisotropy and DMI in Fe5-xGeTe2 flakes with varying thicknesses. Our findings provide a deeper understanding of the magneto-transport behavior of the exotic magnetic structure in 2D ferromagnetic materials, which may benefit future spintronic device applications.
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Affiliation(s)
- Weiting Miao
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
- Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, Anhui, China
| | - Weili Zhen
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Cheng Tan
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Jie Wang
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Yong Nie
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Hengning Wang
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Lan Wang
- Lab of Low Dimensional Magnetism and Spintronic Devices, School of Physics, Hefei University of Technology, Hefei 230009, Anhui, China
| | - Qun Niu
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Mingliang Tian
- High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, Anhui, China
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Ahn HB, Jung SG, Lim H, Kim K, Kim S, Park TE, Park T, Lee C. Giant coercivity enhancement in a room-temperature van der Waals magnet through substitutional metal-doping. NANOSCALE 2023. [PMID: 37357947 DOI: 10.1039/d3nr00681f] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
FexGeTe2 (x = 3, 4, and 5) systems, two-dimensional (2D) van der Waals (vdW) ferromagnetic (FM) metals with high Curie temperatures (TC), have been intensively studied to realize all-2D spintronic devices. Recently, an intrinsic FM material Fe3GaTe2 with high TC (350-380 K) has been reported. As substitutional doping changes the magnetic properties of vdW magnets, it can be a powerful means for engineering the properties of magnetic materials. Here, the coercive field (Hc) is substantially enhanced by substituting Ni for Fe in (Fe1-xNix)3GaTe2 crystals. The introduction of a Ni dopant with x = 0.03 can enhance the value of Hc up to ∼200% while maintaining the FM state at room temperature. As the doping level increases, TC decreases, whereas Hc increases up to 7 kOe at x = 0.12, which is the highest Hc reported so far. The FM characteristic is almost suppressed at x = 0.68 and a spin glass state appears. The enhancement of Hc resulting from Ni doping can be attributed to domain pinning induced by substitutional Ni atoms, as evidenced by the decrease in magnetic anisotropy energy in the crystals upon Ni doping. Our findings provide a highly effective way to control the Hc of the 2D vdW FM metal Fe3GaTe2 for the realization of Fe3GaTe2 based room-temperature operating spintronic devices.
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Affiliation(s)
- Hyo-Bin Ahn
- SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 16419, Korea
| | - Soon-Gil Jung
- Department of Physics Education, Sunchon National University, Suncheon 57922, Korea
| | - Hyungjong Lim
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea.
| | - Kwangsu Kim
- Department of Physics, University of Ulsan, Ulsan 44619, Korea
- Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Korea
| | - Sanghoon Kim
- Department of Physics, University of Ulsan, Ulsan 44619, Korea
| | - Tae-Eon Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Korea
| | - Tuson Park
- Center for Quantum Materials and Superconductivity (CQMS), Sungkyunkwan University, Suwon 16419, Korea.
- Department of Physics, Sungkyunkwan University, Suwon, 16419, Korea
| | - Changgu Lee
- SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 16419, Korea
- School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea.
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