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1.
Nano Lett ; 24(2): 733-740, 2024 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-38166427

RESUMO

The Hall effect has played a vital role in unraveling the intricate properties of electron transport in solid materials. Here, we report on a crystal symmetry-dependent in-plane Hall effect (CIHE) observed in a CuPt/CoPt ferromagnetic heterostructure. Unlike the planar Hall effect (PHE), the CIHE in CuPt/CoPt strongly depends on the current flowing direction (ϕI) with respect to the crystal structure. It reaches its maximum when the current is applied along the low crystal-symmetry axes and vanishes when applied along the high crystal-symmetry axes, exhibiting an unconventional angular dependence of cos(3ϕI). Utilizing a symmetry analysis based on the Invariant Theory, we demonstrate that the CIHE can exist in magnetic crystals possessing C3v symmetry. Using a tight-binding model and realistic first-principles calculations on the metallic heterostructure, we find that the CIHE originates from the trigonal warping of the Fermi surface. Our observations highlight the critical role of crystal symmetry in generating new types of Hall effects.

2.
Environ Sci Technol ; 58(18): 7743-7757, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38652822

RESUMO

Permeabilities of various trace elements (TEs) through the blood-follicle barrier (BFB) play an important role in oocyte development. However, it has not been comprehensively described as well as its involved biological pathways. Our study aimed to construct a blood-follicle distribution model of the concerned TEs and explore their related biological pathways. We finally included a total of 168 women from a cohort of in vitro fertilization-embryo transfer conducted in two reproductive centers in Beijing City and Shandong Province, China. The concentrations of 35 TEs in both serum and follicular fluid (FF) samples from the 168 women were measured, as well as the multiomics features of the metabolome, lipidome, and proteome in both plasma and FF samples. Multiomics features associated with the transfer efficiencies of TEs through the BFB were selected by using an elastic net model and further utilized for pathway analysis. Various machine learning (ML) models were built to predict the concentrations of TEs in FF. Overall, there are 21 TEs that exhibited three types of consistent BFB distribution characteristics between Beijing and Shandong centers. Among them, the concentrations of arsenic, manganese, nickel, tin, and bismuth in FF were higher than those in the serum with transfer efficiencies of 1.19-4.38, while a reverse trend was observed for the 15 TEs with transfer efficiencies of 0.076-0.905, e.g., mercury, germanium, selenium, antimony, and titanium. Lastly, cadmium was evenly distributed in the two compartments with transfer efficiencies of 0.998-1.056. Multiomics analysis showed that the enrichment of TEs was associated with the synthesis and action of steroid hormones and the glucose metabolism. Random forest model can provide the most accurate predictions of the concentrations of TEs in FF among the concerned ML models. In conclusion, the selective permeability through the BFB for various TEs may be significantly regulated by the steroid hormones and the glucose metabolism. Also, the concentrations of some TEs in FF can be well predicted by their serum levels with a random forest model.


Assuntos
Aprendizado de Máquina , Oligoelementos , Humanos , Oligoelementos/metabolismo , Feminino , Líquido Folicular/metabolismo , Líquido Folicular/química , China , Multiômica
3.
Phys Rev Lett ; 124(21): 217202, 2020 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-32530667

RESUMO

We report on the study of both perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interaction (DMI) at an oxide/ferromagnetic metal (FM) interface, i.e., BaTiO_{3} (BTO)/CoFeB. Thanks to the functional properties of the BTO film and the capability to precisely control its growth, we are able to distinguish the dominant role of the oxide termination (TiO_{2} vs BaO) from the moderate effect of ferroelectric polarization in the BTO film, on the PMA and DMI at an oxide/FM interface. We find that the interfacial magnetic anisotropy energy of the BaO-BTO/CoFeB structure is 2 times larger than that of the TiO_{2}-BTO/CoFeB, while the DMI of the TiO_{2}-BTO/CoFeB interface is larger. We explain the observed phenomena by first principles calculations, which ascribe them to the different electronic states around the Fermi level at oxide/ferromagnetic metal interfaces and the different spin-flip process. This study paves the way for further investigation of the PMA and DMI at various oxide/FM structures and thus their applications in the promising field of energy-efficient devices.

4.
Sensors (Basel) ; 20(15)2020 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-32751291

RESUMO

Based on the shift of the Bragg wavelength, fiber Bragg grating (FBG) sensors have been employed to measure a variety of physical parameters such as stress, strain, displacement, temperature, vibration and pressure. In this work, a simple and easy way to be implemented FBG sensing methodology was proposed to measure the temperature and strain simultaneously. Half of the FBG was bonded on the host structure, while the other half of the FBG was left free. The host structure was an aluminum test specimen with dimensions of 20 × 3.8 × 0.5 cm3. As the host structure subjected to mechanical and thermal loadings, the Bragg wavelengths reflected from the bonded and unbonded FBGs are different. Theoretical predictions of the Bragg wavelength shifts of the bonded and unbonded FBGs were presented. Utilizing the Bragg wavelength shift of unbonded FBG, the temperature can be determined and is independent of mechanical strain. The Bragg wavelength shift of the bonded FBG allows the determination of the mechanical strain. The temperature measured by FBG sensor was compared with the result from a thermocouple, while the mechanical strain was validated with the theoretical prediction. Good agreement between the experimental measurement and theoretical prediction demonstrates that temperature-strain discrimination can be realized using the proposed method with one single FBG sensor.

5.
Small ; 12(6): 802-9, 2016 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-26707567

RESUMO

Integrating nanomaterials with different dimensionalities and properties is a versatile approach toward realizing new functionalities in advanced devices. Here, a novel diode-type heterostructure is reported consisting of 1D semiconducting ZnO nanorods and 2D metallic LaAlO3-SrTiO3 interface. Tunable insulator-to-metal transitions, absent in the individual components, are observed as a result of the competing temperature-dependent conduction mechanisms. Detailed transport analysis reveals direct tunneling at low bias, Fowler-Nordheim tunneling at high forward bias, and Zener breakdown at high reverse bias. Our results highlight the rich electronic properties of such artificial diodes with hybrid dimensionalities, and the design principle may be generalized to other nanomaterials.

6.
Front Endocrinol (Lausanne) ; 15: 1345067, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38544690

RESUMO

Background: Mandibuloacral dysplasia (MAD) syndrome is a rare genetic disease. Several progeroid syndromes including mandibuloacral dysplasia type A (MADA), mandibuloacral dysplasia type B(MADB), Hutchinson-Gilford progeria (HGPS) and mandibular hypoplasia, deafness, and lipodystrophy syndrome (MDPL) have been reported previously. A novel MAD progeroid syndrome (MADaM) has recently been reported. So far, 7 cases of MADaM diagnosed with molecular diagnostics have been reported in worldwide. In the Chinese population, cases of MAD associated with the MTX2 variant have never been reported. Methods: The clinical symptoms and the genetic analysis were identified and investigated in patients presented with the disease. In addition, we analyzed and compared 7 MADaM cases reported worldwide and summarized the progeroid syndromes reported in the Chinese population to date. Results: The present study reports a case of a novel homozygous mutation c.378 + 1G > A in the MTX2 gene, which has not been previously reported in the literature. Patients present with early onset and severe symptoms and soon after birth are found to have growth retardation. In addition to the progeroid features, skeletal deformities, generalized lipodystrophy reported previously, and other multisystem involvement, e.g. hepatosplenic, renal, and cardiovascular system, this case was also reported to have combined hypogammaglobulinemia. She has since been admitted to the hospital several times for infections. Among 22 previously reported progeroid syndromes, 16/22 were MADA or HGPS caused by LMNA gene mutations, and the homozygous c.1579C > T (p.R527C) mutation may be a hot spot mutation for MAD in the Chinese population. MAD and HGPS mostly present in infancy with skin abnormalities or alopecia, MDPL mostly presents in school age with growth retardation as the first manifestation, and is often combined with an endocrine metabolism disorder after several decades. Conclusion: This is the first case of MAD syndrome caused by mutations in MTX2 gene reported in the Chinese population. MTX2 gene c.378 + 1G > A homozygous mutation has not been previously reported and the report of this patient expands the spectrum of MTX2 mutations. In addition, we summarized the genotypes and clinical characteristics of patients with progeroid syndromes in China.


Assuntos
Lipodistrofia , Progéria , Feminino , Humanos , Progéria/genética , Progéria/complicações , Progéria/diagnóstico , Lipodistrofia/genética , Síndrome , Mutação , Doenças Raras , Transtornos do Crescimento/complicações
7.
Nat Sci Sleep ; 16: 359-368, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38617037

RESUMO

Background: Pediatric obstructive sleep apnea (OSA) is a multifaceted disorder marked by recurrent upper airway obstruction during sleep, often coexisting with various medical conditions. This study, aimed to comprehensively analyze the Multifaceted Landscape of Pediatric Insights into Prevalence, Severity, and Coexisting Conditions. With a sample of 1928 participants, our study sought to determine the prevalence, severity, and associations between OSA and diverse conditions. Methods: Conducted retrospectively from February 2019 to April 2023, the study included pediatric patients. Data were collected through electronic health records, involving clinical assessments, medical histories, and diagnostic tests to establish OSA and coexisting condition diagnoses. Relationships between sleep parameters, apnea types, and severity indices were evaluated. Results: High OSA prevalence was evident across age groups, with severity peaking between 3 to 12 years. Among the participants, coexisting conditions included allergic rhinitis (59.6%), tonsillar hypertrophy (49.7%), adenoid hypertrophy (28.4%), and obesity (15.3%). Analysis revealed intriguing relationships between different sleep parameters and apnea types. Notable associations were observed between Obstructive Apnea (OA) and Central Apnea (CA), and Mixed Apnea (MA) displayed associations with both OA and CA. Hypopnea correlated directly with the Apnea-Hypopnea Index (AHI), reflecting its role in OSA severity. Conclusion: This study provides a comprehensive understanding of the intricate dynamics between pediatric OSA and coexisting conditions. The prevalence of OSA and its coexistence with various conditions underscore the need for comprehensive evaluation and management strategies. By revealing associations between different sleep parameters and apnea types, the study emphasizes the complexity of OSA diagnosis and management. These findings hold the potential to enhance clinical approaches, ultimately leading to improved care and outcomes for affected children.

8.
Environ Pollut ; 347: 123679, 2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38462199

RESUMO

Close relationships exist between metal(loid)s exposure and embryo implantation failure (EIF) from animal and epidemiological studies. However, there are still inconsistent results and lacking of sensitive metal(loid) exposure biomarkers associated with EIF risk. We aimed to ascertain sensitive metal(loid) biomarkers to EIF and provide potential biological explanations. Candidate metal(loid) biomarkers were measured in the female hair (FH), female serum (FS), and follicular fluid (FF) with various exposure time periods. An analytical framework was established by integrating epidemiological association results, comprehensive literature searching, and knowledge-based adverse outcome pathway (AOP) networks. The sensitive biomarkers of metal(loid)s along with potential biological pathways to EIF were identified in this framework. Among the concerned 272 candidates, 45 metal(loid)s biomarkers across six time periods and three biomatrix were initially identified by single-metal(loid) analyses. Two biomarkers with counterfactual results according to literature summary results were excluded, and a total of five biomarkers were further determined from 43 remained candidates in mixture models. Finally, four sensitive metal(loid) biomarkers were eventually assessed by overlapping AOP networks information, including Se and Co in FH, and Fe and Zn in FS. AOP networks also identified key GO pathways and proteins involved in regulation of oxygen species biosynthetic, cell proliferation, and inflammatory response. Partial dependence results revealed Fe in FS and Co in FH at their low levels might be potential sensitive exposure levels for EIF. Our study provided a typical framework to screen the crucial metal(loid) biomarkers and ascertain that Se and Co in FH, and Fe and Zn in FS played an important role in embryo implantation.


Assuntos
Metaloides , Metais Pesados , Animais , Feminino , Metais/toxicidade , Metais/análise , Implantação do Embrião , Biomarcadores , Cabelo/química , Metais Pesados/análise , Monitoramento Ambiental , Metaloides/análise , China , Medição de Risco
9.
Nanoscale ; 15(2): 820-827, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36533700

RESUMO

Interconversion between charge and spin through spin-orbit coupling at a heavy metal (HM)/ferromagnet (FM) interface plays a key role in determining the amplitude of spin Hall magnetoresistance (SMR), which might maximally facilitate its applications in novel electronics. In this study, annealed NiFe films grown on MgO (100) substrates capped with Pt and Ta are reported to exhibit a maximum SMR. When the measuring temperature is reduced, the SMR rises and is significantly larger in crystalline NiFe than in amorphous NiFe. Another physical process for the negative SMR in Ta(dTa)/Pt(3 nm)/annealed NiFe samples is attributed to the interfacial spin-orbit coupling (ISOC) driven spin current (Js) generation and its reciprocal effects. Moreover, spin accumulation is enhanced at Pt(3 nm)/annealed NiFe interfaces after capping with a Ta layer, which functions as a spin sink in a certain thinner thickness range. With the cooperative interaction of choosing the proper Ta's thickness and annealing NiFe layers, the maximum SMR is obtained. Our results pave the way for rational interface engineering to enhance SMR for developing high-efficiency spintronic devices.

10.
Front Neurol ; 14: 1320954, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38178888

RESUMO

Obstructive sleep apnea (OSA) is a common syndrome characterized by upper airway dysfunction during sleep. Continuous positive airway pressure (CPAP) is the most frequently utilized non-surgical treatment for OSA. Ferroptosis play a crucial role in the physiological diseases caused by chronic intermittent hypoxia, but its involvement in the development of OSA and the exact mechanisms have incompletely elucidated. GSE75097 microarray dataset was used to identify differentially expressed genes between OSA patients and CPAP-treated OSA patients. Subsequently, Gene Ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, STRING database, and FerrDb database were conducted to analyze the biological functions of differentially expressed genes and screen ferroptosis-related genes. Finally, GSE135917 dataset employed for validation. There were 1,540 differentially expressed genes between OSA patients and CPAP-treated OSA patients. These differentially expressed genes were significantly enriched in the regulation of interleukin-1-mediated signaling pathway and ferroptosis-related signaling pathway. Subsequently, 13 ferroptosis-related genes (DRD5, TSC22D3, TFAP2A, STMN1, DDIT3, MYCN, ELAVL1, JUN, DUSP1, MIB1, PSAT1, LCE2C, and MIR27A) were identified from the interaction between differentially expressed genes and FerrDb database, which are regarded as the potential targets of CPAP-treated OSA. These ferroptosis-related genes were mainly involved in cell proliferation and apoptosis and MAPK signaling pathway. Furthermore, DRD5 and TFAP2A were downregulated in OSA patients, which showed good diagnostic properties for OSA, but these abnormal signatures are not reversed with short-term effective CPAP therapy. In summary, the identification of 13 ferroptosis-related genes as potential targets for the CPAP treatment of OSA provides valuable insights into the development of novel, reliable, and accurate therapeutic options.

11.
Nat Commun ; 14(1): 1780, 2023 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-36997572

RESUMO

Ferroelectric hafnia-based thin films have attracted intense attention due to their compatibility with complementary metal-oxide-semiconductor technology. However, the ferroelectric orthorhombic phase is thermodynamically metastable. Various efforts have been made to stabilize the ferroelectric orthorhombic phase of hafnia-based films such as controlling the growth kinetics and mechanical confinement. Here, we demonstrate a key interface engineering strategy to stabilize and enhance the ferroelectric orthorhombic phase of the Hf0.5Zr0.5O2 thin film by deliberately controlling the termination of the bottom La0.67Sr0.33MnO3 layer. We find that the Hf0.5Zr0.5O2 films on the MnO2-terminated La0.67Sr0.33MnO3 have more ferroelectric orthorhombic phase than those on the LaSrO-terminated La0.67Sr0.33MnO3, while with no wake-up effect. Even though the Hf0.5Zr0.5O2 thickness is as thin as 1.5 nm, the clear ferroelectric orthorhombic (111) orientation is observed on the MnO2 termination. Our transmission electron microscopy characterization and theoretical modelling reveal that reconstruction at the Hf0.5Zr0.5O2/ La0.67Sr0.33MnO3 interface and hole doping of the Hf0.5Zr0.5O2 layer resulting from the MnO2 interface termination are responsible for the stabilization of the metastable ferroelectric phase of Hf0.5Zr0.5O2. We anticipate that these results will inspire further studies of interface-engineered hafnia-based systems.

12.
Adv Sci (Weinh) ; 9(30): e2203006, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35927016

RESUMO

Owing to programmable nonlinear dynamics, magnetic domain wall (DW)-based devices can be configured to function as spintronic neurons, promising to execute sophisticated tasks as a human brain. Developing energy-efficient, CMOS compatible, reliable, and tunable spintronic neurons to emulate brain-inspired processes has been a key research goal for decades. Here, a new type of DW device is reported with biological neuron characteristics driven by the synergistic interaction between spin-orbit torque and built-in field (Hbuilt-in ) in magnetic tunnel junctions, enabling time- and energy-efficient leaky-integrate-and-fire and self-reset neuromorphic implementations. A tilted magnetic anisotropic free layer is proposed and further executed to mitigate the DW retrograde motion by suppressing the Walker breakdown. Complementary experiments and micromagnetic co-simulation results show that the integrating/leaking time of the developed spintronic neuron can be tuned to 12/15 ns with an integrating power consumption of 65 µW, which is 36× and 1.84× time and energy efficient than the state-of-the-art alternatives, respectively. Moreover, the spatial distribution of Hbuilt-in can be modulated by adjusting the width and compensation of the reference layer, facilitating tunable activation function generator exploration. Such architecture demonstrates great potential in both fundamental research and new trajectories of technology advancement for spintronic neuron hardware applications.


Assuntos
Redes Neurais de Computação , Sinapses , Humanos , Sinapses/fisiologia , Anisotropia , Torque , Neurônios/fisiologia , Fenômenos Magnéticos
13.
Nat Commun ; 13(1): 3539, 2022 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-35725723

RESUMO

All-electric switching of perpendicular magnetization is a prerequisite for the integration of fast, high-density, and low-power magnetic memories and magnetic logic devices into electric circuits. To date, the field-free spin-orbit torque (SOT) switching of perpendicular magnetization has been observed in SOT bilayer and trilayer systems through various asymmetric designs, which mainly aim to break the mirror symmetry. Here, we report that the perpendicular magnetization of CoxPt100-x single layers within a special composition range (20 < x < 56) can be deterministically switched by electrical current in the absence of external magnetic field. Specifically, the Co30Pt70 shows the largest out-of-plane effective field efficiency and best switching performance. We demonstrate that this unique property arises from the cooperation of two structural mechanisms: the low crystal symmetry property at the Co platelet/Pt interfaces and the composition gradient along the thickness direction. Compared with that in bilayers or trilayers, the field-free switching in CoxPt100-x single layer greatly simplifies the SOT structure and avoids additional asymmetric designs.

14.
Adv Mater ; 34(33): e2109449, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35751473

RESUMO

Van der Waals materials are attracting great attention in the field of spintronics due to their novel physical properties. For example, they are utilized as spin-current generating materials in spin-orbit torque (SOT) devices, which offers an electrical way to control the magnetic state and is promising for future low-power electronics. However, SOTs have mostly been demonstrated in vdW materials with strong spin-orbit coupling (SOC). Here, the observation of a current-induced SOT in the h-BN/SrRuO3 bilayer structure is reported, where the vdW material (h-BN) is an insulator with negligible SOC. Importantly, this SOT is strong enough to induce the switching of the perpendicular magnetization in SrRuO3 . First-principles calculations suggest a giant Rashba effect at the interface between vdW material and SrRuO3 (110)pc thin film, which leads to the observed SOT based on a simplified tight-binding model. Furthermore, it is demonstrated that the current-induced magnetization switching can be modulated by the electric field. This study paves the way for exploring the current-induced SOT and magnetization switching by integrating vdW materials with ferromagnets.

15.
ACS Nano ; 16(1): 1436-1443, 2022 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-34918901

RESUMO

Quantum spin Hall (QSH) systems hold promises of low-power-consuming spintronic devices, yet their practical applications are extremely impeded by the small energy gaps. Fabricating QSH materials with large gaps, especially under the guidance of design principles, is essential for both scientific research and practical applications. Here, we demonstrate that large on-site atomic spin-orbit coupling can be directly exploited via the intriguing substrate-orbital-filtering effect to generate large-gap QSH systems and experimentally realized on the epitaxially synthesized ultraflat bismuthene on Ag(111). Theoretical calculations reveal that the underlying substrate selectively filters Bi pz orbitals away from the Fermi level, leading pxy orbitals with nonzero magnetic quantum numbers, resulting in large topological gap of ∼1 eV at the K point. The corresponding topological edge states are identified through scanning tunneling spectroscopy combined with density functional theory calculations. Our findings provide general strategies to design large-gap QSH systems and further explore their topology-related physics.

16.
PLoS One ; 16(9): e0256879, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34499691

RESUMO

This paper uses event study based on the Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model to study the impact of the COVID-19 outbreak on China's financial market. It finds that the pandemic had an overall significant and negative impact on the stock prices of firms listed on SSE, SZSE and ChiNext. However, such impact appeared to be heterogeneous across industries, affecting listed firms in industries such as pharmaceutical and telecommunications positively, but those in services industries such as accommodation, catering, and commercial services negatively. Apparently, a crisis for some had been an opportunity for others. In addition, this paper seeks to understand the micro mechanism behind the heterogeneity of pandemic shock from the perspective of firms' financial position. It finds that listed firms with higher debt level were hit harder, whereas those with more net cash flow had displayed higher resilience against the blow of the pandemic. However, the opposite pattern is found among those listed on ChiNext and in industries severely devastated by the pandemic. These findings have policy implications in terms of preventing systemic financial risks and facilitating recovery during pandemic-induced economic downturns. It also helps investor adjust investment strategies, hedge against risks, and secure gains when the market conditions in general are unfavorable.


Assuntos
COVID-19/economia , COVID-19/epidemiologia , Modelos Econômicos , China/epidemiologia , Administração Financeira , Indústrias , Investimentos em Saúde
17.
ACS Appl Mater Interfaces ; 13(15): 18294-18300, 2021 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-33822573

RESUMO

Current-induced spin-orbit torque (SOT) switching of magnetization has attracted great interest due to its potential application in magnetic memory devices, which offer low-energy consumption and high-speed writing. However, most of the SOT studies on perpendicularly magnetized anisotropy (PMA) magnets have been limited to heterostructures with interfacial PMA and poor thermal stability. Here, we experimentally demonstrate a SOT magnetization switching for a ferrimagnetic D022-Mn3Ge film with high bulk PMA and robust thermal stability factor under a critical current density of 6.6 × 1011 A m-2 through the spin Hall effect of an adjacent capping Pt and a buffer Cr layer. A large effective damping-like SOT efficiency of 2.37 mT/1010 A m-2 is determined using harmonic measurements in the structure. The effect of the double-spin source layers and the negative-exchange interaction of the ferrimagnet may explain the large SOT efficiency and the manifested magnetization switching of Mn3Ge. Our findings demonstrate that D022-Mn3Ge is a promising candidate for application in high-density SOT magnetic random-access memory devices.

18.
Adv Mater ; 33(36): e2103672, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34302404

RESUMO

Neuromorphic computing has become an increasingly popular approach for artificial intelligence because it can perform cognitive tasks more efficiently than conventional computers. However, it remains challenging to develop dedicated hardware for artificial neural networks. Here, a simple bilayer spintronic device for hardware implementation of neuromorphic computing is demonstrated. In L11 -CuPt/CoPt bilayer, current-inducted field-free magnetization switching by symmetry-dependent spin-orbit torques shows a unique domain nucleation-dominated magnetization reversal, which is not accessible in conventional bilayers. Gradual domain nucleation creates multiple intermediate magnetization states which form the basis of a sigmoidal neuron. Using the L11 -CuPt/CoPt bilayer as a sigmoidal neuron, the training of a deep learning network to recognize written digits, with a high recognition rate (87.5%) comparable to simulation (87.8%) is further demonstrated. This work offers a new scheme of implementing artificial neural networks by magnetic domain nucleation.


Assuntos
Cobalto/química , Cobre/química , Aprendizado Profundo , Platina/química , Algoritmos , Simulação por Computador , Sistemas Computacionais , Redes Neurais de Computação , Neurônios , Torque
19.
Adv Mater ; 33(30): e2007114, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34145647

RESUMO

Spin-orbit torque (SOT), which arises from the spin-orbit coupling of conduction electrons, is believed to be the key route for developing low-power, high-speed, and nonvolatile memory devices. Despite the theoretical prediction of pronounced Berry phase curvatures in certain transition-metal perovskite oxides, which lead to considerable intrinsic spin Hall conductivity, SOT from this class of materials has rarely been reported until recently. Here, the SOT generated by epitaxial SrRuO3 of three different crystal structures is systematically studied. The results of both spin-torque ferromagnetic resonance and in-plane harmonic Hall voltage measurements concurrently reveal that the intrinsic SOT efficiency of SrRuO3 decreases when the epitaxial strain changes from tensile to compressive. The X-ray diffraction data demonstrate a strong correlation between the magnitude of SOT and octahedral rotation around the in-plane axes of SrRuO3 , consistent with the theoretical prediction. This work offers new possibilities of tuning SOT with crystal structures and novel opportunities of integrating the unique properties of perovskite oxides with spintronic functionalities.

20.
Sci Adv ; 7(13)2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33762343

RESUMO

Although the phenomenon of tunneling has been known since the advent of quantum mechanics, it continues to enrich our understanding of many fields of science. Commonly, this effect is described in terms of electrons traversing the potential barrier that exceeds their kinetic energy due to the wave nature of electrons. This picture of electron tunneling fails, however, for tunnel junctions, where the Fermi energy lies sufficiently close to the insulator valence band, in which case, hole tunneling dominates. We demonstrate the deterministic control of electron and hole tunneling in interface-engineered Pt/BaTiO3/La0.7Sr0.3MnO3 ferroelectric tunnel junctions by reversal of tunneling electroresistance. Our electrical measurements, electron microscopy and spectroscopy characterization, and theoretical modeling unambiguously point out to electron or hole tunneling regimes depending on interface termination. The interface control of the tunneling regime offers designed functionalities of electronic devices.

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