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Spin direction dependent quantum anomalous Hall effect in two-dimensional ferromagnetic materials

Yu-Xian Yang(杨宇贤) and Chang-Wen Zhang(张昌文)

Chin. Phys. B, 2024, 33 (4): 047101. DOI: 10.1088/1674-1056/ad1380

Abstract （22）

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We propose a scheme for realizing the spin direction-dependent quantum anomalous Hall effect (QAHE) driven by spin—orbit couplings (SOC) in two-dimensional (2D) materials. Based on the sp³ tight-binding (TB) model, we find that these systems can exhibit a QAHE with out-of-plane and in-plane magnetization for the weak and strong SOC, respectively, in which the mechanism of quantum transition is mainly driven by the band inversion of p_x,y/p_z orbitals. As a concrete example, based on first-principles calculations, we realize a real material of monolayer 1T-SnN₂/PbN₂ exhibiting the QAHE with in-plane/out-of-plane magnetization characterized by the nonzero Chern number C and topological edge states. These findings provide useful guidance for the pursuit of a spin direction-dependent QAHE and hence stimulate immediate experimental interest.

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Research of caged dynamics of clusters center atoms in Pd₈₂Si₁₈ amorphous alloy

Yong-He Deng(邓永和), Bei Chen(陈贝), Qing-Hua Qi(祁清华), Bing-Bing Li(李兵兵), Ming Gao(高明), Da-Dong Wen(文大东), Xiao-Yun Wang(王小云), and Ping Peng(彭平)

Chin. Phys. B, 2024, 33 (4): 047102. DOI: 10.1088/1674-1056/ad1d4e

Abstract （24）

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To date, there is still a lack of a comprehensive explanation for caged dynamics which is regarded as one of the intricate dynamic behaviors in amorphous alloys. This study focuses on Pd₈₂Si₁₈ as the research object to further elucidate the underlying mechanism of caged dynamics from multiple perspectives, including the cage's lifetime, atomic local environment, and atomic potential energy. The results reveal that Si atoms exhibit a pronounced cage effect due to the hindrance of Pd atoms, resulting in an anomalous peak in the non-Gaussian parameters. An in-depth investigation was conducted on the caged dynamics differences between fast and slow Si atoms. In comparison to fast Si atoms, slow Si atoms were surrounded by more Pd atoms and occupied lower potential energy states, resulting in smaller diffusion displacements for the slow Si atoms. Concurrently, slow Si atoms tend to be in the centers of smaller clusters with coordination numbers of 9 and 10. During the isothermal relaxation process, clusters with coordination numbers 9 and 10 have longer lifetimes, suggesting that the escape of slow Si atoms from their cages is more challenging. The findings mentioned above hold significant implications for understanding the caged dynamics.

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Actively tuning anisotropic light—matter interaction in biaxial hyperbolic material α-MoO₃ using phase change material VO₂ and graphene

Kun Zhou(周昆), Yang Hu(胡杨), Biyuan Wu(吴必园), Xiaoxing Zhong(仲晓星), and Xiaohu Wu(吴小虎)

Chin. Phys. B, 2024, 33 (4): 047103. DOI: 10.1088/1674-1056/ad23d2

Abstract （23）

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Anisotropic hyperbolic phonon polaritons (PhPs) in natural biaxial hyperbolic material α-MoO₃ has opened up new avenues for mid-infrared nanophotonics, while active tunability of α-MoO₃ PhPs is still an urgent problem necessarily to be solved. In this study, we present a theoretical demonstration of actively tuning α-MoO₃ PhPs using phase change material VO₂ and graphene. It is observed that α-MoO₃ PhPs are greatly dependent on the propagation plane angle of PhPs. The insulator-to-metal phase transition of VO₂ has a significant effect on the hybridization PhPs of the α-MoO₃/VO₂ structure and allows to obtain actively tunable α-MoO₃ PhPs, which is especially obvious when the propagation plane angle of PhPs is 90°. Moreover, when graphene surface plasmon sources are placed at the top or bottom of α-MoO₃ in α-MoO₃/VO₂ structure, tunable coupled hyperbolic plasmon—phonon polaritons inside its Reststrahlen bands (RBs) and surface plasmon—phonon polaritons outside its RBs can be achieved. In addition, the above-mentioned α-MoO₃-based structures also lead to actively tunable anisotropic spontaneous emission (SE) enhancement. This study may be beneficial for realization of active tunability of both PhPs and SE of α-MoO₃, and facilitate a deeper understanding of the mechanisms of anisotropic light—matter interaction in α-MoO₃ using functional materials.

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Anisotropic spin transport and photoresponse characteristics detected by tip movement in magnetic single-molecule junction

Deng-Hui Chen(陈登辉), Zhi Yang(羊志), Xin-Yu Fu(付新宇), Shen-Ao Qin(秦申奥), Yan Yan(严岩), Chuan-Kui Wang(王传奎), Zong-Liang Li(李宗良), and Shuai Qiu(邱帅)

Chin. Phys. B, 2024, 33 (4): 047201. DOI: 10.1088/1674-1056/ad1e65

Abstract （23）

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Orientation-dependent transport properties induced by anisotropic molecules are enticing in single-molecule junctions. Here, using the first-principles method, we theoretically investigate spin transport properties and photoresponse characteristics in trimesic acid magnetic single-molecule junctions with different molecular adsorption orientations and electrode contact sites. The transport calculations indicate that a single-molecule switch and a significant enhancement of spin transport and photoresponse can be achieved when the molecular adsorption orientation changes from planar geometry to upright geometry. The maximum spin polarization of current and photocurrent in upright molecular junctions exceeds 90%. Moreover, as the Ni tip electrode moves, the tunneling magnetoresistance of upright molecular junctions can be increased to 70%. The analysis of the spin-dependent PDOS elucidates that the spinterfaces between organic molecule and ferromagnetic electrodes are modulated by molecular adsorption orientation, where the molecule in upright molecular junctions yields higher spin polarization. Our theoretical work paves the way for designing spintronic devices and optoelectronic devices with anisotropic functionality base on anisotropic molecules.

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Spin-polarized pairing induced by the magnetic field in the Bernal bilayer graphene

Yan Huang(黄妍) and Tao Zhou(周涛)

Chin. Phys. B, 2024, 33 (4): 047403. DOI: 10.1088/1674-1056/ad102f

Abstract （28）

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Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field. In this study, we conduct a theoretical investigation of the potential pairing symmetry within this superconducting system. By developing a theoretical model, we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing, p+ip-wave anti-parallel spin pairing and d+id-wave pairing symmetry. Our results confirm that the magnetic field is indeed essential for generating the superconductivity. We discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the system. The numerical calculations of the energy band structure, zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.

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Analytical solutions to the precession relaxation of magnetization with uniaxial anisotropy

Ze-Nan Zhang(张泽南), Zhen-Lin Jia(贾镇林), and De-Sheng Xue(薛德胜)

Chin. Phys. B, 2024, 33 (4): 047502. DOI: 10.1088/1674-1056/ad08a3

Abstract （19）

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Based on the Landau--Lifshitz--Gilbert (LLG) equation, the precession relaxation of magnetization is studied when the external field ${{\bm H}}$ is parallel to the uniaxial anisotropic field ${{\bm H}}_{\rm k}$. The evolution of three-component magnetization is solved analytically under the condition of $H=nH_{\rm k}$ ($n =3$, 1 and 0). It is found that with an increase of ${{\bm H}}$ or a decrease of the initial polar angle of magnetization, the relaxation time decreases and the angular frequency of magnetization increases. For comparison, the analytical solution for $H_{\rm k}=0$ is also given. When the magnetization becomes stable, the angular frequency is proportional to the total effective field acting on the magnetization. The analytical solutions are not only conducive to the understanding of the precession relaxation of magnetization, but also can be used as a standard model to test the numerical calculation of LLG equation.

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Wedge-shaped HfO₂ buffer layer-induced field-free spin—orbit torque switching of HfO₂/Pt/Co structure

Jian-Hui Chen(陈建辉), Meng-Fan Liang(梁梦凡), Yan Song(宋衍), Jun-Jie Yuan(袁俊杰), Meng-Yang Zhang(张梦旸), Yong-Ming Luo(骆泳铭), and Ning-Ning Wang(王宁宁)

Chin. Phys. B, 2024, 33 (4): 047503. DOI: 10.1088/1674-1056/ad1a88

Abstract （28）

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Field-free spin—orbit torque (SOT) switching of perpendicular magnetization is essential for future spintronic devices. This study demonstrates the field-free switching of perpendicular magnetization in an HfO₂/Pt/Co/TaO_x structure, which is facilitated by a wedge-shaped HfO₂ buffer layer. The field-free switching ratio varies with HfO₂ thickness, reaching optimal performance at 25 nm. This phenomenon is attributed to the lateral anisotropy gradient of the Co layer, which is induced by the wedge-shaped HfO₂ buffer layer. The thickness gradient of HfO₂ along the wedge creates a corresponding lateral anisotropy gradient in the Co layer, correlating with the switching ratio. These findings indicate that field-free SOT switching can be achieved through designing buffer layer, offering a novel approach to innovating spin—orbit device.

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Enhanced stability of FA-based perovskite: Rare-earth metal compound EuBr₂ doping

Minna Hou(候敏娜), Xu Guo(郭旭), Meidouxue Han(韩梅斗雪), Juntao Zhao(赵均陶), Zhiyuan Wang(王志元), Yi Ding(丁毅), Guofu Hou(侯国付), Zongsheng Zhang(张宗胜), and Xiaoping Han(韩小平)

Chin. Phys. B, 2024, 33 (4): 047802. DOI: 10.1088/1674-1056/ad23d5

Abstract （38）

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It is highly desirable to enhance the long-term stability of perovskite solar cells (PSCs) so that this class of photovoltaic cells can be effectively used for the commercialization purposes. In this contribution, attempts have been made to use the two-step sequential method to dope EuBr₂ into FAMAPbI₃ perovskite to promote the stability. It is shown that the device durability at 85 ℃ in air with RH of 20%—40% is improved substantially, and simultaneously the champion device efficiency of 23.04% is achieved. The enhancement in stability is attributed to two points: (i) EuBr₂ doping effectively inhibits the decomposition and α—δ phase transition of perovskite under ambient environment, and (ii) EuBr₂ aggregates in the oxidized format of Eu(BrO₃)₃ at perovskite grain boundaries and surface, hampering humidity erosion and mitigates degradation through coordination with H₂O.

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Physical mechanism of secondary-electron emission in Si wafers

Yanan Zhao(赵亚楠), Xiangzhao Meng(孟祥兆), Shuting Peng(彭淑婷), Guanghui Miao(苗光辉), Yuqiang Gao(高玉强), Bin Peng(彭斌), Wanzhao Cui(崔万照), and Zhongqiang Hu(胡忠强)

Chin. Phys. B, 2024, 33 (4): 047901. DOI: 10.1088/1674-1056/ad1175

Abstract （26）

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CMOS-compatible RF/microwave devices, such as filters and amplifiers, have been widely used in wireless communication systems. However, secondary-electron emission phenomena often occur in RF/microwave devices based on silicon (Si) wafers, especially in the high-frequency range. In this paper, we have studied the major factors that influence the secondary-electron yield (SEY) in commercial Si wafers with different doping concentrations. We show that the SEY is suppressed as the doping concentration increases, corresponding to a relatively short effective escape depth λ. Meanwhile, the reduced narrow band gap is beneficial in suppressing the SEY, in which the absence of a shallow energy band below the conduction band will easily capture electrons, as revealed by first-principles calculations. Thus, the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.

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Effects of vacancy and external electric field on the electronic properties of the MoSi₂N₄/graphene heterostructure

Qian Liang(梁前), Xiangyan Luo(罗祥燕), Guolin Qian(钱国林), Yuanfan Wang(王远帆), Yongchao Liang(梁永超), and Quan Xie(谢泉)

Chin. Phys. B, 2024, 33 (3): 037101. DOI: 10.1088/1674-1056/acef04

Abstract （38）

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Recently, the newly synthesized septuple-atomic layer two-dimensional (2D) material MoSi₂N₄ (MSN) has attracted attention worldwide. Our work delves into the effect of vacancies and external electric fields on the electronic properties of the MSN/graphene (Gr) heterostructure using first-principles calculation. We find that four types of defective structures, N-in, N-out, Si and Mo vacancy defects of monolayer MSN and MSN/Gr heterostructure are stable in air. Moreover, vacancy defects can effectively modulate the charge transfer at the interface of the MSN/Gr heterostructure as well as the work function of the pristine monolayer MSN and MSN/Gr heterostructure. Finally, the application of an external electric field enables the dynamic switching between n-type and p-type Schottky contacts. Our work may offer the possibility of exceeding the capabilities of conventional Schottky diodes based on MSN/Gr heterostructures.

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Exciton-polaritons in a 2D hybrid organic-inorganic perovskite microcavity with the presence of optical Stark effect

Kenneth Coker, Chuyuan Zheng(郑楚媛), Joseph Roger Arhin, Kwame Opuni-Boachie Obour Agyekum, and Weili Zhang(张伟利)

Chin. Phys. B, 2024, 33 (3): 037102. DOI: 10.1088/1674-1056/ad1484

Abstract （36）

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This study investigates the properties of exciton-polaritons in a two-dimensional (2D) hybrid organic-inorganic perovskite microcavity in the presence of optical Stark effect. Through both steady and dynamic state analyses, strong coupling between excitons of perovskite and cavity photons is revealed, indicating the formation of polaritons in the perovskite microcavity. Besides, it is found that an external optical Stark pulse can induce energy shifts of excitons proportional to the pulse intensity, which modifies the dispersion characteristics of the polaritons.

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Effect of electron-electron interaction on polarization process of exciton and biexciton in conjugated polymer

Xiao-Xue Li(李晓雪), Hua Peng(彭华), Dong Wang(王栋), and Dong Hou(侯栋)

Chin. Phys. B, 2024, 33 (3): 037201. DOI: 10.1088/1674-1056/ad0bf1

Abstract （36）

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By using one-dimensional tight-binding model modified to include electron-electric field interaction and electron-electron interaction, we theoretically explore the polarization process of exciton and biexciton in cis-polyacetylene. The dynamical simulation is performed by adopting the non-adiabatic evolution approach. The results show that under the effect of moderate electric field, when the strength of electron-electron interaction is weak, the singlet exciton is stable but its polarization presents obvious oscillation. With the enhancement of interaction, it is dissociated into polaron pairs, the spin-flip of which can be observed through modulating the interaction strength. For the triplet exciton, the strong electron-electron interaction restrains its normal polarization, but it is still stable. In the case of biexciton, the strong electron-electron interaction not only dissociate it, but also flip its charge distribution. The yield of the possible states formed after the dissociation of exciton and biexciton is also calculated.

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Negative magnetoresistance in the antiferromagnetic semimetal V_1/3TaS₂

Zi Wang(王子), Xin Peng(彭馨), Shengnan Zhang(张胜男), Yahui Su(苏亚慧), Shaodong Lai(赖少东), Xuan Zhou(周旋), Chunxiang Wu(吴春翔), Tingyu Zhou(周霆宇), Hangdong Wang(王杭栋), Jinhu Yang(杨金虎), Bin Chen(陈斌), Huifei Zhai(翟会飞), Quansheng Wu(吴泉生), Jianhua Du(杜建华), Zhiwei Jiao(焦志伟), and Minghu Fang(方明虎)

Chin. Phys. B, 2024, 33 (3): 037301. DOI: 10.1088/1674-1056/ad18aa

Abstract （43）

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Intercalated transition metal dichalcogenides (TMDCs) attract much attention due to their rich properties and potential applications. In this article, we grew successfully high-quality V_1/3TaS₂ crystals by a vapor transport method. We measured the magnetization, longitudinal resistivity ρ_xx(T, H), Hall resistivity ρ_xy(T, H), as well as performed calculations of the electronic band structure. It was found that V_1/3TaS₂ is an A-type antiferromagnet with the Neel temperature T_N = 6.20 K, and exhibits a negative magnetoresistance (MR) near T_N. Both band structure calculations and Hall resistivity measurements demonstrated it is a magnetic semimetal.

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Exploring reservoir computing: Implementation via double stochastic nanowire networks

Jian-Feng Tang(唐健峰), Lei Xia(夏磊), Guang-Li Li(李广隶), Jun Fu(付军), Shukai Duan(段书凯), and Lidan Wang(王丽丹)

Chin. Phys. B, 2024, 33 (3): 037302. DOI: 10.1088/1674-1056/aceeea

Abstract （37）

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Neuromorphic computing, inspired by the human brain, uses memristor devices for complex tasks. Recent studies show that self-organizing random nanowires can implement neuromorphic information processing, enabling data analysis. This paper presents a model based on these nanowire networks, with an improved conductance variation profile. We suggest using these networks for temporal information processing via a reservoir computing scheme and propose an efficient data encoding method using voltage pulses. The nanowire network layer generates dynamic behaviors for pulse voltages, allowing time series prediction analysis. Our experiment uses a double stochastic nanowire network architecture for processing multiple input signals, outperforming traditional reservoir computing in terms of fewer nodes, enriched dynamics and improved prediction accuracy. Experimental results confirm the high accuracy of this architecture on multiple real-time series datasets, making neuromorphic nanowire networks promising for physical implementation of reservoir computing.

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Coexistence of antiferromagnetism and unconventional superconductivity in a quasi-one-dimensional flat-band system: Creutz lattice

Feng Xu(徐峰) and Lei Zhang(张磊)

Chin. Phys. B, 2024, 33 (3): 037402. DOI: 10.1088/1674-1056/acf5d2

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We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime. The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model, the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory. An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction, while antiferromagnetism accompanies this state. The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase. The A phase is analogous to the pseudogap phase, which shows that electrons go to form pairs but do not cause a supercurrent. We also show the superfluid behavior of the unconventional superconducting state and its critical temperature. It is proven directly that the flat band can effectively raise the critical temperature of superconductivity. It is implementable to simulate and control strongly-correlated electrons' behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures. Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.

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Mechanical and magnetocaloric adjustable properties of Fe₃O₄/PET deformed nanoparticle film

Fengguo Fan(范凤国) and Lintong Duan(段林彤)

Chin. Phys. B, 2024, 33 (3): 037502. DOI: 10.1088/1674-1056/acf280

Abstract （28）

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The flexibility of nanoparticle films is a topic of rapidly growing interest in both scientific and engineering researches due to their numerous potential applications in a broad range of wearable electronics and biomedical devices. This article presents the elucidation of the properties of nanoparticle films. Here, a flexible film is fabricated based on polyethylene terephthalate (PET) and magnetic iron oxide at the nanoscale using layer-by-layer technology. The 2D thin flexible film material can be bent at different angles from 0° to 360°. With an increase in elastic deformation angles, the magnetocaloric effect of the film gradually increases in the alternating magnetic field. The test results from a vibrating sample magnetometer and a low-frequency impedance analyzer demonstrate that the film has a good magnetic response and anisotropy. The magnetocaloric effect and magnetic induction effect are controlled by deformation, providing a new idea for the application of elastic films. It combines the flexibility of the nanoparticle PET substrate and, in the future, it may be used for skin adhesion for administration and magnetic stimulation control.

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Interacting topological magnons in a checkerboard ferromagnet

Heng Zhu(朱恒), Hongchao Shi(施洪潮), Zhengguo Tang(唐政国), and Bing Tang(唐炳)

Chin. Phys. B, 2024, 33 (3): 037503. DOI: 10.1088/1674-1056/ad01a2

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This work is devoted to studying the magnon-magnon interaction effect in a two-dimensional checkerboard ferromagnet with the Dzyaloshinskii-Moriya interaction. Using a first-order Green function method, we analyze the influence of magnon-magnon interaction on the magnon band topology. We find that Chern numbers of two renormalized magnon bands are different above and below the critical temperature, which means that the magnon band gap-closing phenomenon is an indicator for one topological phase transition of the checkerboard ferromagnet. Our results show that the checkerboard ferromagnet possesses two topological phases, and its topological phase can be controlled either via the temperature or the applied magnetic field due to magnon-magnon interactions. Interestingly, it is found that the topological phase transition can occur twice with the increase in the temperature, which is different from the results of the honeycomb ferromagnet.

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Unconventional room-temperature negative magnetoresistance effect in Au/n-Ge:Sb/Au devices

Xiong He(何雄), Fan-Li Yang(杨凡黎), Hao-Yu Niu(牛浩峪), Li-Feng Wang(王立峰), Li-Zhi Yi(易立志),Yun-Li Xu(许云丽), Min Liu(刘敏), Li-Qing Pan(潘礼庆), and Zheng-Cai Xia(夏正才)

Chin. Phys. B, 2024, 33 (3): 037504. DOI: 10.1088/1674-1056/ad15f8

Abstract （77）

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Non-magnetic semiconductor materials and their devices have attracted wide attention since they are usually prone to exhibit large positive magnetoresistance (MR) effect in a low static magnetic field environment at room temperature. However, how to obtain a large room-temperature negative MR effect in them remains to be studied. In this paper, by designing an Au/n-Ge:Sb/Au device with metal electrodes located on identical side, we observe an obvious room-temperature negative MR effect in a specific 50 T pulsed high magnetic field direction environment, but not in a static low magnetic field environment. Through the analysis of the experimental measurement of the Hall effect results and bipolar transport theory, we propose that this unconventional negative MR effect is mainly related to the charge accumulation on the surface of the device under the modulation of the stronger Lorentz force provided by the pulsed high magnetic field. This theoretical analytical model is further confirmed by regulating the geometry size of the device. Our work sheds light on the development of novel magnetic sensing, magnetic logic and other devices based on non-magnetic semiconductors operating in pulsed high magnetic field environment.

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Spin gap in quasi-one-dimensional S=3/2 antiferromagnet CoTi₂O₅

Hao-Hang Xu(徐浩航), Qing-Yuan Liu(刘庆元), Chao Xin(辛潮), Qin-Xin Shen(申沁鑫), Jun Luo(罗军), Rui Zhou(周睿), Jin-Guang Cheng(程金光), Jian Liu(刘健), Ling-Ling Tao(陶玲玲), Zhi-Guo Liu(刘志国), Ming-Xue Huo(霍明学), Xian-Jie Wang(王先杰), and Yu Sui(隋郁)

Chin. Phys. B, 2024, 33 (3): 037505. DOI: 10.1088/1674-1056/ad1381

Abstract （59）

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Quasi-one-dimensional (1D) antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra. Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi₂O₅ with highly ordered Co²⁺/Ti⁴⁺ occupation, in which the Co²⁺ ions with S=3/2 form a 1D spin chain along the a-axis. CoTi₂O₅ undergoes an antiferromagnetic transition at T_N ~ 24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region. Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins, by analyzing the specific heat, the thermal conductivity, and the spin-lattice relaxation rate (1/T₁) as a function of temperature, we found that a spin gap is opened in the spin-excitation spectrum of CoTi₂O₅ around T_N, manifested by the rapid decrease of magnetic specific heat to zero, the double-peak characteristic in thermal conductivity, and the exponential decay of 1/T₁ below T_N. Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi₂O₅, which induces the magnetic anisotropy in CoTi₂O₅, and then opens the spin gap at low temperature.

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Enhanced resonance frequency in Co₂FeAl thin film with different thicknesses grown on flexible graphene substrate

Cai Zhou(周偲), Shaokang Yuan(袁少康), Dengyu Zhu(朱登玉), Yuming Bai(白宇明), Tao Wang(王韬), Fufu Liu(刘福福), Lulu Pan(潘禄禄), Cunfang Feng(冯存芳), Bohan Zhang(张博涵), Daping He(何大平), and Shengxiang Wang(汪胜祥)

Chin. Phys. B, 2024, 33 (3): 037506. DOI: 10.1088/1674-1056/acfafa

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The flexible materials exhibit more favorable properties than most rigid substrates in flexibility, weight saving, mechanical reliability, and excellent environmental toughness. Particularly, flexible graphene film with unique mechanical properties was extensively explored in high frequency devices. Herein, we report the characteristics of structure and magnetic properties at high frequency of Co₂FeAl thin film with different thicknesses grown on flexible graphene substrate at room temperature. The exciting finding for the columnar structure of Co₂FeAl thin film lays the foundation for excellent high frequency property of Co₂FeAl/flexible graphene structure. In-plane magnetic anisotropy field varying with increasing thickness of Co₂FeAl thin film can be obtained by measurement of ferromagnetic resonance, which can be ascribed to the enhancement of crystallinity and the increase of grain size. Meanwhile, the resonance frequency which can be achieved by the measurement of vector network analyzer with the microstrip method increases with increasing thickness of Co₂FeAl thin film. Moreover, in our case with graphene film, the resonance magnetic field is quite stable though folded for twenty cycles, which demonstrates that good flexibility of graphene film and the stability of high frequency magnetic property of Co₂FeAl thin film grown on flexible graphene substrate. These results are promising for the design of microwave devices and wireless communication equipment.

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