Anomalous electrons in a metallic kagome ferromagnet.

Ordinary metals contain electron liquids within well-defined 'Fermi' surfaces at which the electrons behave as if they were non-interacting. In the absence of transitions to entirely new phases such as insulators or superconductors, interactions between electrons induce scattering that is quadratic in the deviation of the binding energy from the Fermi level. A long-standing puzzle is that certain materials do not fit this 'Fermi liquid' description. A common feature is strong interactions between electrons relative to their kinetic energies. One route to this regime is special lattices to reduce the electron kinetic energies. Twisted bilayer graphene1-4 is an example, and trihexagonal tiling lattices (triangular 'kagome'), with all corner sites removed on a 2 × 2 superlattice, can also host narrow electron bands5 for which interaction effects would be enhanced. Here we describe spectroscopy revealing non-Fermi-liquid behaviour for the ferromagnetic kagome metal Fe3Sn2 (ref. 6). We discover three C3-symmetric electron pockets at the Brillouin zone centre, two of which are expected from density functional theory. The third and most sharply defined band emerges at low temperatures and binding energies by means of fractionalization of one of the other two, most likely on the account of enhanced electron-electron interactions owing to a flat band predicted to lie just above the Fermi level. Our discovery opens the topic of how such many-body physics involving flat bands7,8 could differ depending on whether they arise from lattice geometry or from strongly localized atomic orbitals9,10.

Tunable Magnetism in Atomically Thin Itinerant Antiferromagnet with Room-Temperature Ferromagnetic Order.

Addressing the need for modulated spin configurations is crucial, as they serve as the foundational building blocks for next-generation spintronics, particularly in atomically thin structures and at room temperature. In this work, we realize intrinsic ferromagnetism in monolayer flakes and tunable ferro-/antiferromagnetism in (Fe0.56Co0.44)5GeTe2 antiferromagnets. Remarkably, the ferromagnetic ordering (≥1 L) and antiferromagnetic ordering (≥4 L) remain discernible up to room temperature. The TC (∼310 K) of the monolayer flakes sets a record high for known exfoliated monolayer van der Waals magnets. Within the framework of A-type antiferromagnetism, a notable odd-even layer-number effect at elevated temperatures (T = 150 K) is observed. Of particular interest is the strong ferromagnetic order in even-layer flakes at low temperatures. The intricate interplay among magnetic field strength, layer number, and temperature gives rise to a diverse array of phenomena, holding promise not only for new physics but also for practical applications.

Reactive Oxygen Species-Responsive Delivery of a Notch Inhibitor to Alleviate Nonalcoholic Steatohepatitis by Inhibiting Hepatic de Novo Lipogenesis and Inflammation.

With the increased prevalence of nonalcoholic steatohepatitis (NASH) in the world, effective pharmacotherapy in clinical practice is still lacking. Previous studies have shown that dibenzazepine (DBZ), a Notch inhibitor, could alleviate NASH development in a mouse model. However, low bioavailability, poor water solubility, and extrahepatic side effects restrict its clinical application. To overcome these barriers, we developed a reactive oxygen species (ROS)-sensitive nanoparticle based on the conjugation of bilirubin to poly(ethylene glycol) (PEG) chains, taking into account the overaccumulation of hepatic ROS in the pathologic state of nonalcoholic steatohepatitis (NASH). The PEGylated bilirubin can self-assemble into nanoparticles in an aqueous solution and encapsulate insoluble DBZ into its hydrophobic cavity. DBZ nanoparticles (DBZ Nps) had good stability, rapidly released DBZ in response to H2O2, and effectively scavenged intracellular ROS of hepatocytes. After systemic administration, DBZ Nps could accumulate in the liver of the NASH mice, extend persistence in circulation, and improve the bioavailability of DBZ. Furthermore, DBZ Nps significantly improved glucose intolerance, relieved hepatic lipid accumulation and inflammation, and ameliorated NASH-induced liver fibrosis. Additionally, DBZ Nps had no significant extrahepatic side effects. Taken together, our results highlight the potential of the ROS-sensitive DBZ nanoparticle as a promising therapeutic strategy for NASH.

Multiple mobile excitons manifested as sidebands in quasi-one-dimensional metallic TaSe3.

Charge neutrality and their expected itinerant nature makes excitons potential transmitters of information. However, exciton mobility remains inaccessible to traditional optical experiments that only create and detect excitons with negligible momentum. Here, using angle-resolved photoemission spectroscopy, we detect dispersing excitons in the quasi-one-dimensional metallic trichalcogenide, TaSe3. The low density of conduction electrons and the low dimensionality in TaSe3 combined with a polaronic renormalization of the conduction band and the poorly screened interaction between these polarons and photo-induced valence holes leads to various excitonic bound states that we interpret as intrachain and interchain excitons, and possibly trions. The thresholds for the formation of a photo-hole together with an exciton appear as side valence bands with dispersions nearly parallel to the main valence band, but shifted to lower excitation energies. The energy separation between side and main valence bands can be controlled by surface doping, enabling the tuning of certain exciton properties.

Electric Control of Exchange Bias Effect in FePS3-Fe5GeTe2 van der Waals Heterostructures.

Manipulating the exchange bias (EB) effect using an electronic gate is a significant goal in spintronics. The emergence of van der Waals (vdW) magnetic heterostructures has provided improved means to study interlayer magnetic coupling, but to date, these heterostructures have not exhibited electrical gate-controlled EB effects. Here, we report electrically controllable EB effects in a vdW heterostructure, FePS3-Fe5GeTe2. By applying a solid protonic gate, the EB effects were repeatably electrically tuned. The EB field reaches up to 23% of the coercivity and the blocking temperature ranges from 30 to 60 K under various gate-voltages. The proton intercalations not only tune the average magnetic exchange coupling but also change the antiferromagnetic configurations in the FePS3 layer. These result in a dramatic modulation of the total interface exchange coupling and the resultant EB effects. The study is a significant step toward vdW heterostructure-based magnetic logic for future low-energy electronics.

Gate-Controlled Magnetic Phase Transition in a van der Waals Magnet Fe5GeTe2.

Magnetic van der Waals (vdW) materials are poised to enable all-electrical control of magnetism in the two-dimensional limit. However, tuning the magnetic ground state in vdW itinerant ferromagnets by voltage-induced charge doping remains a significant challenge, due to the extremely large carrier densities in these materials. Here, by cleaving the vdW itinerant ferromagnet Fe5GeTe2 (F5GT) into 5.4 nm (around two unit cells), we find that the ferromagnetism (FM) in F5GT can be substantially tuned by the thickness. Moreover, by utilizing a solid protonic gate, an electron doping concentration of above 1021 cm-3 has been exhibited in F5GT nanosheets. Such a high carrier accumulation exceeds that possible in widely used electric double-layer transistors (EDLTs) and surpasses the intrinsic carrier density of F5GT. Importantly, it is accompanied by a magnetic phase transition from FM to antiferromagnetism (AFM). The realization of an antiferromagnetic phase in nanosheet F5GT suggests the promise of applications in high-temperature antiferromagnetic vdW devices and heterostructures.

Gate-Tuned Interlayer Coupling in van der Waals Ferromagnet Fe_{3}GeTe_{2} Nanoflakes.

The weak interlayer coupling in van der Waals (vdW) magnets has confined their application to two dimensional (2D) spintronic devices. Here, we demonstrate that the interlayer coupling in a vdW magnet Fe_{3}GeTe_{2} (FGT) can be largely modulated by a protonic gate. With the increase of the protons intercalated among vdW layers, interlayer magnetic coupling increases. Because of the existence of antiferromagnetic layers in FGT nanoflakes, the increasing interlayer magnetic coupling induces exchange bias in protonated FGT nanoflakes. Most strikingly, a rarely seen zero-field cooled (ZFC) exchange bias with very large values (maximally up to 1.2 kOe) has been observed when higher positive voltages (V_{g}≥4.36 V) are applied to the protonic gate, which clearly demonstrates that a strong interlayer coupling is realized by proton intercalation. Such strong interlayer coupling will enable a wider range of applications for vdW magnets.

Origin of Magnetism in Hydrothermally Aged 2-Line Ferrihydrite Suspensions.

As an iron oxyhydroxide, nanosized ferrihydrite (Fh) is important in Earth science, biology, and industrial applications. However, its basic structure and origin of its magnetism have long been debated. We integrate synchrotron-based techniques to explore the chemical structures of 2-line ferrihydrite and to determine the origin of its magnetism during hydrothermal aging in air. Our results demonstrate that both the magnetism and X-ray magnetic circular dichroism (XMCD) signal of 2-line ferrihydrite are enhanced with aging time, and that XMCD spectral patterns resemble that of maghemite (γ-Fe2O3) rather than magnetite (Fe3O4). Fe L-edge and K-edge X-ray absorption spectroscopy (XAS) further indicate formation of both maghemite and hematite (α-Fe2O3) with increasing concentrations with longer hydrothermal aging time. Thus, magnetic enhancement with longer hydrothermal aging time is attributed to increasing maghemite concentration instead of a magnetically ordered ferrihydrite as previously reported. Moreover, L-edge and K-edge XAS spectra with different probing depths yield different ratios of these Fe oxides, which suggest the formation of a core (ferrihydrite-rich)-shell (with a mixture of both allotropes; α-Fe2O3 and γ-Fe2O3) structure during hydrothermal aging. Our results provide insights into the chemical evolution of 2-line ferrihydrite that reveal unambiguously the origin of its magnetism.

Interfacial electronic structures revealed at the rubrene/CH3NH3PbI3 interface.

The electronic structures of rubrene films deposited on CH3NH3PbI3 perovskite have been investigated using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). It was found that rubrene molecules interacted weakly with the perovskite substrate. Due to charge redistribution at their interface, a downward 'band bending'-like energy shift of ∼0.3 eV and an upward band bending of ∼0.1 eV were identified at the upper rubrene side and the CH3NH3PbI3 substrate side, respectively. After the energy level alignment was established at the rubrene/CH3NH3PbI3 interface, its highest occupied molecular orbital (HOMO)-valence band maximum (VBM) offset was found to be as low as ∼0.1 eV favoring the hole extraction with its lowest unoccupied molecular orbital (LUMO)-conduction band minimum (CBM) offset as large as ∼1.4 eV effectively blocking the undesired electron transfer from perovskite to rubrene. As a demonstration, simple inverted planar solar cell devices incorporating rubrene and rubrene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers (HTLs) were fabricated in this work and yielded a champion power conversion efficiency of 8.76% and 13.52%, respectively. Thus, the present work suggests that a rubrene thin film could serve as a promising hole transport layer for efficient perovskite-based solar cells.

Anomalous surface lattice dynamics in the low-temperature phase of Ba(Fe1-xCox)2As2.

In complex materials, how correlation between charge, spin, and lattice affects the emergent phenomena remains unclear. The newly discovered iron-based high-temperature superconductors and related compounds present to the community a prototype family of materials, where interplay between charge, spin, and lattice degrees of freedom can be explored. With the occurrence of structural, magnetic, and superconducting transitions in the bulk of these materials, creating a surface will change the delicate balance between these phases, resulting in new behavior. A surface lattice dynamics study on (001) Ba(Fe(1-x)Co(x))(2)As(2), through electron energy loss spectroscopy measurements, reveals unusual temperature dependence of both the phonon frequency and line width in the low-temperature orthorhombic phase. The rate of change of phonon frequency with temperature is gigantic, two orders of magnitude larger than in the bulk. This behavior cannot be explained using conventional models of anharmonicity or electron-phonon coupling; instead, it requires that a large surface-spin-charge-lattice coupling be included. Furthermore, the higher surface-phase-transition temperature driven by surface stabilization of the low-temperature orthorhombic phase seems to turn the first-order transition (bulk) into the second-order type, equivalent to what is observed in the bulk by applying a uniaxial pressure. Such equivalence indicates that the surface mirrors the bulk under extreme conditions.

Dualistic insulator states in 1T-TaS2 crystals.

While the monolayer sheet is well-established as a Mott-insulator with a finite energy gap, the insulating nature of bulk 1T-TaS2 crystals remains ambiguous due to their varying dimensionalities and alterable interlayer coupling. In this study, we present a unique approach to unlock the intertwined two-dimensional Mott-insulator and three-dimensional band-insulator states in bulk 1T-TaS2 crystals by structuring a laddering stack along the out-of-plane direction. Through modulating the interlayer coupling, the insulating nature can be switched between band-insulator and Mott-insulator mechanisms. Our findings demonstrate the duality of insulating nature in 1T-TaS2 crystals. By manipulating the translational degree of freedom in layered crystals, our discovery presents a promising strategy for exploring fascinating physics, independent of their dimensionality, thereby offering a "three-dimensional" control for the era of slidetronics.

CREKA-modified liposomes target activated hepatic stellate cells to alleviate liver fibrosis by inhibiting collagen synthesis and angiogenesis.

Activated hepatic stellate cells (HSCs) are considered the key driver of excessive extracellular matrix and abnormal angiogenesis, which are the main pathological manifestations of hepatic fibrosis. However, the absence of specific targeting moieties has rendered the development of HSC-targeted drug delivery systems a significant obstacle in the treatment of liver fibrosis. Here we have identified a notable increase in fibronectin expression on HSCs, which positively correlates with the progression of hepatic fibrosis. Thus, we decorated PEGylated liposomes with CREKA, a peptide with high affinity for fibronectin, to facilitate the targeted delivery of sorafenib to activated HSCs. The CREKA-coupled liposomes exhibited enhanced cellular uptake in the human hepatic stellate cell line LX2 and selective accumulation in CCl4-induced fibrotic liver through the recognition of fibronectin. When loaded with sorafenib, the CREKA-modified liposomes effectively suppressed HSC activation and collagen accumulation in vitro. Furthermore. in vivo results demonstrated that the administration of sorafenib-loaded CREKA-liposomes at a low dose significantly mitigated CCl4-induced hepatic fibrosis, prevented inflammatory infiltration and reduced angiogenesis in mice. These findings suggest that CREKA-coupled liposomes have promising potential as a targeted delivery system for therapeutic agents to activated HSCs, thereby providing an efficient treatment option for hepatic fibrosis. STATEMENT OF SIGNIFICANCE: In liver fibrosis, activated hepatic stellate cells (aHSCs) are the key driver of extracellular matrix and abnormal angiogenesis. Our investigation has revealed a significant elevation in fibronectin expression on aHSCs, which is positively associated with the progression of hepatic fibrosis. Thus, we developed PEGylated liposomes decorated with CREKA, a molecule with a high affinity for fibronectin, to facilitate the targeted delivery of sorafenib to aHSCs. The CREKA-coupled liposomes can specifically target aHSCs both in vitro and in vivo. Loading sorafenib into CREKA-Lip significantly alleviated CCl4-induced liver fibrosis, angiogenesis and inflammation at low doses. These findings suggest that our drug delivery system holds promise as a viable therapeutic option for liver fibrosis with minimal risk of adverse effects.

Electric-field control of reversible electronic and magnetic transitions in two-dimensional oxide monolayer magnets.

Atomically thin oxide magnetic materials are highly desirable due to the promising potential to integrate two-dimensional (2D) magnets into next-generation spintronics. Therefore, 2D oxide magnetism is expected to be effectively tuned by the magnetic and electrical fields, holding prospective for future low-dissipation electronic devices. However, the electric-field control of 2D oxide monolayer magnetism has rarely been reported. Here, we present the realization of 2D monolayer magnetism in oxide (SrRuO3)1/(SrTiO3)N (N = 1, 3) superlattices that shows an efficient and reversible phase transition through electric-field controlled proton (H+) evolution. By using ionic liquid gating to modulate the proton concentration in (SrRuO3)1/(SrTiO3)1 superlattice, an electric-field induced metal-insulator transition was observed, along with gradually suppressed magnetic ordering and modulated magnetic anisotropy. Theoretical analysis reveals that proton intercalation plays a crucial role in both electronic and magnetic phase transitions. Strikingly, SrTiO3 layers can act as a proton sieve, which have a significant influence on proton evolution. Our work stimulates the tuning functionality of 2D oxide monolayer magnetism by voltage control, providing potential for future energy-efficient electronics.

Dually fibronectin/CD44-mediated nanoparticles targeted disrupt the Golgi apparatus and inhibit the hedgehog signaling in activated hepatic stellate cells to alleviate liver fibrosis.

Liver fibrosis is featured by activation of hepatic stellate cells (HSCs) and excessive accumulation of extracellular matrix (ECM). The Golgi apparatus in HSCs plays a vital role in synthesis and secretion of ECM proteins, while its targeted disruption in activated HSCs could be considered as a promising approach for liver fibrosis treatment. Here, we developed a multitask nanoparticle CREKA-CS-RA (CCR) to specifically target the Golgi apparatus of activated HSCs, based on CREKA (a specific ligand of fibronectin) and chondroitin sulfate (CS, a major ligand of CD44), in which retinoic acid (a Golgi apparatus-disturbing agent) chemically conjugated and vismodegib (a hedgehog inhibitor) encapsulated. Our results showed that CCR nanoparticles specifically targeted activated HSCs and preferentially accumulated in the Golgi apparatus. Systemic administration of CCR nanoparticles exhibited significantly accumulation in CCl4-induced fibrotic liver, which was attributed to specific recognition with fibronectin and CD44 on activated HSCs. CCR nanoparticles loaded with vismodegib not only disrupted Golgi apparatus structure and function but also inhibited the hedgehog signaling pathway, thus markedly suppressing HSC activation and ECM secretion in vitro and in vivo. Moreover, vismodegib-loaded CCR nanoparticles effectively inhibited the fibrogenic phenotype in CCl4-induced liver fibrosis mice without causing obvious toxicity. Collectively, these findings indicate that this multifunctional nanoparticle system can effectively deliver therapeutic agents to the Golgi apparatus of activated HSCs, thus has potential treatment of liver fibrosis with minimal side effects.

Glutaredoxin 1 regulates cholesterol metabolism and gallstone formation by influencing protein S-glutathionylation.

OBJECTIVE: Cholesterol gallstone disease (CGD) is closely related to cholesterol metabolic disorder. Glutaredoxin-1 (Glrx1) and Glrx1-related protein S-glutathionylation are increasingly being observed to drive various physiological and pathological processes, especially in metabolic diseases such as diabetes, obesity and fatty liver. However, Glrx1 has been minimally explored in cholesterol metabolism and gallstone disease. METHODS: We first investigated whether Glrx1 plays a role in gallstone formation in lithogenic diet-fed mice using immunoblotting and quantitative real-time PCR. Then a whole-body Glrx1-deficient (Glrx1-/-) mice and hepatic-specific Glrx1-overexpressing (AAV8-TBG-Glrx1) mice were generated, in which we analyzed the effects of Glrx1 on lipid metabolism upon LGD feeding. Quantitative proteomic analysis and immunoprecipitation (IP) of glutathionylated proteins were performed. RESULTS: We found that protein S-glutathionylation was markedly decreased and the deglutathionylating enzyme Glrx1 was greatly increased in the liver of lithogenic diet-fed mice. Glrx1-/- mice were protected from gallstone disease induced by a lithogenic diet because their biliary cholesterol and cholesterol saturation index (CSI) were reduced. Conversely, AAV8-TBG-Glrx1 mice showed greater gallstone progression with increased cholesterol secretion and CSI. Further studies showed that Glrx1-overexpressing greatly altered bile acid levels and/or composition to increase intestinal cholesterol absorption by upregulating Cyp8b1. In addition, liquid chromatography-mass spectrometry and IP analysis revealed that Glrx1 also affected the function of asialoglycoprotein receptor 1 (ASGR1) by mediating its deglutathionylation, thereby altering the expression of LXRα and controlling cholesterol secretion. CONCLUSION: Our findings present novel roles of Glrx1 and Glrx1-regulated protein S-glutathionylation in gallstone formation through the targeting of cholesterol metabolism. Our data advises Glrx1 significantly increased gallstone formation by simultaneously increase bile-acid-dependent cholesterol absorption and ASGR1- LXRα-dependent cholesterol efflux. Our work suggests the potential effects of inhibiting Glrx1 activity to treat cholelithiasis.

Glutaredoxin-1 alleviates acetaminophen-induced liver injury by decreasing its toxic metabolites.

Excessive N-acetyl-p-benzoquinone imine (NAPQI) formation is a starting event that triggers oxidative stress and subsequent hepatocyte necrosis in acetaminophen (APAP) overdose caused acute liver failure (ALF). S-glutathionylation is a reversible redox post-translational modification and a prospective mechanism of APAP hepatotoxicity. Glutaredoxin-1 (Glrx1), a glutathione-specific thioltransferase, is a primary enzyme to catalyze deglutathionylation. The objective of this study was to explored whether and how Glrx1 is associated with the development of ALF induced by APAP. The Glrx1 knockout mice (Glrx1-/-) and liver-specific overexpression of Glrx1 (AAV8-Glrx1) mice were produced and underwent APAP-induced ALF. Pirfenidone (PFD), a potential inducer of Glrx1, was administrated preceding APAP to assess its protective effects. Our results revealed that the hepatic total protein S-glutathionylation (PSSG) increased and the Glrx1 level reduced in mice after APAP toxicity. Glrx1-/- mice were more sensitive to APAP overdose, with higher oxidative stress and more toxic metabolites of APAP. This was attributed to Glrx1 deficiency increasing the total hepatic PSSG and the S-glutathionylation of cytochrome p450 3a11 (Cyp3a11), which likely increased the activity of Cyp3a11. Conversely, AAV8-Glrx1 mice were defended against liver damage caused by APAP overdose by inhibiting the S-glutathionylation and activity of Cyp3a11, which reduced the toxic metabolites of APAP and oxidative stress. PFD precede administration upregulated Glrx1 expression and alleviated APAP-induced ALF by decreasing oxidative stress. We have identified the function of Glrx1 mediated PSSG in liver injury caused by APAP overdose. Increasing Glrx1 expression may be investigated for the medical treatment of APAP-caused hepatic injury.

Probing the lower limit of lattice thermal conductivity in an ordered extended solid: Gd117Co56Sn112, a phonon glass-electron crystal system.

The discovery of novel materials with low thermal conductivity is paramount to improving the efficiency of thermoelectric devices. As lattice thermal conductivity is inversely linked to unit cell complexity, we set out to synthesize a highly complex crystalline material with glasslike thermal conductivity. Here we present the structure, transport properties, heat capacity, and magnetization of single-crystal Gd(117)Co(56)Sn(112), a complex material with a primitive unit cell volume of ~6858 Å(3) and ~285 atoms per primitive unit cell (1140 atoms per face-centered cubic unit cell). The room temperature lattice thermal conductivity of this material is κ(L) = 0.28 W/(m·K) and represents one of the lowest ever reported for a nonglassy or nonionically conducting bulk solid. Furthermore, this material exhibits low resistivity at room temperature, and thus represents a true physical system that approaches the ideal phonon glass-electron crystal.

RUNX3 directly interacts with intracellular domain of Notch1 and suppresses Notch signaling in hepatocellular carcinoma cells.

RUNX3 takes a strong suppressive effect in many tumors including hepatocellular carcinoma (HCC). HES-1, a downstream target of Notch signaling, is shown to be decreased in human HCC cell line SMMC7721 with RUNX3 gene transfection. Since Notch signaling is oncogenic in HCC, RUNX3 might exert its inhibitory effect in HCC partly through the suppression on Notch signaling. To investigate the possible mechanism of the down-regulation of HES-1 by RUNX3, we performed Western blot and reporter assay and found that RUNX3 suppressed intracellular domain of Notch1 (ICN1)-mediated transactivation of Notch signaling while it did not alter the expression of ICN1 and recombination signal binding protein-J kappa (RBP-J) in SMMC7721 cells. Besides, confocal microscopy, co-immunoprecipitation and GST pull-down assays showed that RUNX3 could co-localize with ICN1 and RBP-J, forming a complex with these two molecules in nucleus of SMMC7721 cells by its direct interaction with ICN1. Furthermore, RUNX3 was recruited to RBP-J recognition motif of HES-1 promoter, which was identified by chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assay (EMSA). Taken together, these findings indicate that RUNX3 suppresses Notch signaling in HCC SMMC7721 cells by its interaction with ICN1 and thus recruitment to the RBP-J recognition motif of downstream genes of Notch signaling.

Current-Controlled Topological Magnetic Transformations in a Nanostructured Kagome Magnet.

Topological magnetic charge Q is a fundamental parameter that describes the magnetic domains and determines their intriguing electromagnetic properties. The ability to switch Q in a controlled way by electrical methods allows for flexible manipulation of electromagnetic behavior in future spintronic devices. Here, the room-temperature current-controlled topological magnetic transformations between Q = -1 skyrmions and Q = 0 stripes or type-II bubbles in a kagome crystal Fe3 Sn2 are reported. It is shown that reproducible and reversible skyrmion-bubble and skyrmion-stripe transformations can be achieved by tuning the density of nanosecond pulsed current of the order of ≈1010 A m-2 . Further numerical simulations suggest that spin-transfer torque combined with Joule thermal heating effects determine the current-induced topological magnetic transformations.

Two-dimensional characterization of three-dimensional magnetic bubbles in Fe3Sn2 nanostructures.

We report differential phase contrast scanning transmission electron microscopy (TEM) of nanoscale magnetic objects in Kagome ferromagnet Fe3Sn2 nanostructures. This technique can directly detect the deflection angle of a focused electron beam, thus allowing clear identification of the real magnetic structures of two magnetic objects including three-ring and complex arch-shaped vortices in Fe3Sn2 by Lorentz-TEM imaging. Numerical calculations based on real material-specific parameters well reproduced the experimental results, showing that the magnetic objects can be attributed to integral magnetizations of two types of complex three-dimensional (3D) magnetic bubbles with depth-modulated spin twisting. Magnetic configurations obtained using the high-resolution TEM are generally considered as two-dimensional (2D) magnetic objects previously. Our results imply the importance of the integral magnetizations of underestimated 3D magnetic structures in 2D TEM magnetic characterizations.