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SiCN thin film is one of the most attractive silicon-based materials due to its excellent electrical, mechanical and optical properties. In this study, SiCN thin films have been prepared by the radio frequency reactive magnetron sputtering method under different sputtering power, pressure, and substrate temperature. The microstructure, morphology, and the optical and field emission properties of SiCN thin films were performed. The results indicated that the high-quality SiCN thin films have been successfully prepared and it is proved that these properties can be tailored by the preparation conditions. A main near ultraviolet light emission line at around 370 nm in SiCN thin films makes it suitable for the development of optoelectronic devices. This study can provide novel guidance for the controlled preparation of high-quality SiCN thin films by magnetron sputtering.

The efforts toward the experimental realization of spin-polarized transports in ideal materials or platforms, such as the magnetized graphene or various quantum Hall states, is a research hotspot in spintronics. Magnetic van der Waals materials open the door for exploring various physical phenomena, technologies, and integrating novel spintronic devices seamlessly within the 2D limit. Here, we demonstrate magnetic proximity effect in chromium trichloride (CrCl3)/bilayer graphene (BLG) heterostructures by low-temperature transport measurements. An effective exchange field induced in BLG has been demonstrated by the Zeeman spin Hall effect via nonlocal measurements. Furthermore, the exchange field modulates the quantum Hall ground state of BLG and thus favors the formation of a canted antiferromagnetic (CAF) phase in an external perpendicular magnetic field (B⊥). Asymmetric nonlocal magneto-transport behaviors are also observed at opposite B⊥ directions, due to the asymmetric modulation on the exchange field by external B⊥ directions. Our work suggests that the 2D magnetic van der Waals materials and graphene hybrid systems offer a unique platform for quantum Hall ferromagnetism physics.

All-solid-state sodium-ion batteries that utilize inorganic superionic conductors show great potential in energy storage applications. However, suitable Na superionic conductors with desirable high ionic conductivities and cross-linked diffusion networks are still in their infancy. In this work, we systematically studied the structural stabilities and Na ion transport mechanisms of the halide-based Na superionic conductors with different phase structures using first-principle calculations and data mining techniques. The iodide-based Na3YI6 with C2/m, Pm1, and P1c space groups possess fcc and hcp anion sublattices with stable octahedral Na occupations, differing from the reported fast-ion transport mechanism in the sulfide bcc anion ones with tetrahedral Na occupations. The Oct–Tet–Oct diffusion pathway and Na-site weighted phonon vibrational frequencies play crucial roles in the synergistic Na-ion transport capabilities, leading to Na ionic conductivities of 0.35, 0.18, and 9.1 × 10−3 mS cm−1 at room temperature and corresponding activation energies of 315.5, 351.1, and 454.0 meV for C2/m-Na3YI6, Pm1-Na3YI6, and P1c-Na3YI6, respectively. Restricted by the decisive diffusion triangle, P1c-Na3YI6 shows deficient Na-kinetic performance with one-dimensional blocked ion transport channels. The phase-structure-dependent ion transport networks involving Oct–Tet and Oct–Oct pathways broaden the diffusion channels and provide rational guidance for the experimental design of halide-based Na superionic conductors.

As an efficient converter between electromagnetic and mechanical energies, magnetostriction is an intriguing property for not only fundamental studies but also technological applications. However, the understanding of its microscopic origin remains challenging, which is critical for the development of magnetostriction materials. Here, the critical role of spin rotation in the giant magnetostriction of La(Fe,Al)13 is first revealed by the in-situ magnetic and temperature field of neutron powder diffraction. The giant magnetostriction originates from magnetic-field-driven spin moment rotation of canting structure, in which the sharp increase of ferromagnetic component causes the elongation of icosahedron inside of lattice. Furthermore, it is the first time to reveal the accurate canting antiferromagnetic structure in La(Fe,Al)13. The present study provides a new strategy, i.e., the spin rotation, for exploring new magnetostriction functional materials.

Negative thermal expansion (NTE) plays an increasingly important role in the control of thermal expansion of materials. However, the discovery of strong NTE materials, which is rare, remains challe...

Self-healing materials, which can autonomously repair damages like living organisms, have undergone extensive development in the last decades. The bottleneck problems for their practical applications are long healing time, inferior mechanical strength, and aging sensitivity. Here, a new class of polymeric materials rationally grafted with oligo poly(ethylene glycol) is reported. The network based on the formation of multiple weak hydrogen bonds endows the elastomers with good comprehensive performances including high stretchability (725%), high strength (4.20 MPa), and fast self-healing process (40 s). Benefiting from characteristic multiple weak hydrogen bond interactions, the fractured elastomers maintain high healing efficiency even after aging for 192 h, showing an unusual aging insensitivity. A Sudoku structural device based on the developed elastomer shows shape memory effect, providing a new avenue for fabricating novel smart devices with complicated shapes.

Numerous efforts in improving the hydrogen evolution reaction (HER) performance of transition metal dichalcogenides mostly focus on active sites exposing, vacancy engineering, and phase engineering...

Pt-based magnetic nanocatalysts are one of the most suitable candidates for electrocatalytic materials due to their high electrochemistry activity and retrievability. Unfortunately, the inferior durability prevents them from being scaled-up, limiting their commercial applications. Herein, an antiferromagnetic element Mn was introduced into PtCo nanostructured alloy to synthesize uniform Mn-PtCo truncated octahedral nanoparticles (TONPs) by one-pot method. Our results show that Mn can tune the blocking temperature of Mn-PtCo TONPs due to its antiferromagnetism. At low temperatures, Mn-PtCo TONPs are ferromagnetic, and the coercivity increases gradually with increasing Mn contents. At room temperature, the Mn-PtCo TONPs display superparamagnetic behavior, which is greatly helpful for industrial recycling. Mn doping can not only modify the electronic structure of PtCo TONPs but also enhance electrocatalytic performance for methanol oxidation reaction. The maximum specific activity of Mn-PtCo-3 reaches 8.1 A·m-2, 3.6 times of commercial Pt/C (2.2 A·m-2) and 1.4 times of PtCo TONPs (5.6 A·m-2), respectively. The mass activity decreases by only 30% after 2,000 cycles, while it is 45% and 99% (nearly inactive) for PtCo TONPs and commercial Pt/C catalysts, respectively.

The hexagonal MM'X alloys with giant magnetocaloric effects have become an important magnetic phase-transition alloy family. Among the studies on this family, various methods, including composition engineering, have been developed to tailor the magnetostructural transitions. In this study, we present an alternative scheme to tailor the magnetostructural transitions by applying high-temperature staged quenching and low-temperature cyclical ageing on the hexagonal MnCoGe-based alloys with unchanged compositions. The experimental results show that the martensitic transition temperature decreases due to the increasing number of thermal vacancies produced in the increasing annealing temperature, which indicates the martensitic transition is strongly dependent on the staged quenching from high temperatures that can tune the concentration of equilibrious thermal vacancies in alloys. As a result, a Curie temperature window is established, in which the coupling of magnetostructural transitions is successfully realized, showing tunable, large magnetocaloric effects. By further applying cyclical ageing at low-temperature region, the magnetostructural transitions and magnetocaloric effects can be tuned to higher temperatures again due to the release of the trapped thermal vacancies, showing a high tunability of the magnetostructural transitions. During these heat treatments, furthermore, the transitions are robust against the high temperatures up to 550 °C, with no decoupling of the structural and magnetic transitions. The present work provides an important, efficient scheme to tailor the magnetostructural transitions, multiple magnetic/structural phase states, and the related functional properties of hexagonal phase-transition alloy family, without changing the chemical composition of the materials.

Magnetic circular dichroism (MCD) and magnetic linear dichroism (MLD) have been investigated in a photoemission electron microscopy (PEEM) system excited by a deep ultra-violet (DUV) laser (with λ = 177.3 nm and hυ = 7.0 eV) for the first time. High resolution PEEM magnetic images (down to 43.2 nm) were directly obtained on a (001)-oriented magnetic FePt film surface with a circularly-polarized light under normal incidence. Furthermore, a stepped Cr seeding layer was applied to induce the formation of large-area epitaxial FePt films with (001) and (111) two orientations, where MLD with large asymmetry was observed in the transition area of two phases. It demonstrates that DUV laser can be a powerful source for high resolution magnetic imaging in the laboratory in absence of synchrotron facilities.

A spintronic device based on the spin-dependent Hall effect has attracted great interest because of its great potential applications in the multivalue storage and logic gate, which is a promising candidate to break the bottleneck of the information industry in the big data period. It is a technological challenge to implant spintronic devices into semiconductor integrated circuits. The anomalous Hall angle (θ), defined as the deviation of the electron flow from the current direction, is the key parameter to evaluate the capacity of Hall device compatibility. However, the bottleneck for the device is low θ (less than 5%) at room temperature (RT), making it difficult to directly complement with the semiconductor circuit which limits its potential application. Here, we report a simple perpendicular multilayered structure with θ up to 5.1% at RT. Wide working temperature (250-350 K) across RT for our samples will accelerate the potential applications in spintronic memory. A giant Hall angle at RT originates from the enhanced side-jump scattering at the atomic-scale-modified interfacial structure. The high θ at RT together with wide working temperature is practically significant and may provide the way for further 3D spintronic devices based on the spin-dependent Hall effect with ultrahigh storage density and ultralow power consumption.

Two-dimensional (2D) materials and van der Waals heterostructures have attracted tremendous attention because of their appealing electronic, mechanical, and optoelectronic properties, which offer the possibility to extend the range of functionalities for diverse potential applications. Here, we fabricate a novel multiterminal device with dual-gate based on 2D material van der Waals heterostructures. Such a multiterminal device exhibited excellent nonvolatile multilevel resistance switching performance controlled by the source-drain voltage and back-gate voltage. Based on these features, heterosynaptic plasticity, in which the synaptic weight can be tuned by another modulatory interneuron, has been mimicked. A tunable analogue weight update (both on/off ratio and update nonlinearity) of synapse with high speed (50 ns) and low energy (∼7.3 fJ) programming has been achieved. These results demonstrate the great potential of the artificial synapse based on van der Waals heterostructures for neuromorphic computing.

Owing to tip effect can introduce localized enhanced electric field and reduce interfacial energy barrier, design of atomic tip structure in single-atom catalysts (SACs) may be a fascinating strategy to further improve its electrocatalytic activity. However, conventional synthesis methods, such as defect-trapping or substitution, only lead to the formation of planar geometry of SACs without tip atoms. Good conductive 1T-TMDs with electrocatalytically active basal plane can provide platform to directly stabilize single atoms (SAs) on the top sites of its surface to form atomic tip structure. Herein, a universal Laser-molecular beam epitaxy (L-MBE) method for precisely controlling non-noble metal SAs directly immobilizing on the Cr top site of 1T-CrS2 metallic basal plane is developed. In case of Mo, the Mo SAs@1T-CrS2 with single-atom tip structure can exhibit enhanced electric field surrounding Mo atoms and an almost zero hydrogen adsorption free energy, resulting in superior HER performance together with high stability. This work provides a general way to design varieties of SACs in widely catalytic application.

A series of single phase Lu1-xCaxFe2O4 (x = 0, 0.05, 0.1) samples were successfully prepared by solid state reaction. The dielectric permittivity/loss at various frequencies and the temperature dependence of the magnetization/resistivity were systematically analyzed. By optimizing Ca-doping, giant dielectric tunability was obtained at low bias electric fields, with great advantages for industrial applications in the near future. Furthermore, the activation energies together with the magnetic moments can be tuned, originating from a variable ratio of Fe2+/Fe3+ by Ca2+ doping. The substitution for Lu3+ by Ca2+ ions provides a novel way to manipulate the dielectric and magnetic properties of charge ordered Lu1-xCaxFe2O4 systems.

The memtranstors employing the magnetoelectric effects have the great potential to develop artificial synaptic devices. We have fabricated a memtranstor made of the FeGa/PMN-PT/FeGa multiferroic heterostructure and used it to mimic the functions of synapses. The magnetoelectric voltage of the device can be continuously tuned by applying a train of electric-field pulses. Consequently, synaptic plasticity, including the long-term potentiation, long-term depression, and spiking-time-dependent plasticity, has been demonstrated in the memtranstor at room temperature. Simulations on a neural network made of an array of the memtranstors reveal the capability of pattern learning with a high accuracy.

By inserting a Gd layer with strong oxygen-affinitive property, the effect of interfacial oxygen migration on the perpendicular magnetic anisotropy (PMA) and damping constant was investigated in perpendicular Ta/CoFeB/Gd/MgO/Ta multilayers. The overoxidation of CoFeB was greatly suppressed by inserting a thin Gd layer at CoFeB/MgO interface, leading to an O-poor status at interface. Different oxygen migration behavior in samples without and with Gd was observed during the thermal annealing. By optimizing Gd thickness, the effective damping constant of 0.029 and 0.037 was obtained with 0.6 nm Gd layer in out-of-plane and in-plane configuration, respectively. This value was decreased by 70% and 46% with respect to that without Gd layer. More importantly, the PMA can be well maintained when Gd thickness was increased to 1.2 nm. This effective modification of magnetic properties based on oxygen migration provides a promising pathway for spintronic applications.

Ferroelectric poly(vinylidene fluoride) (PVDF) nanofilms have been fabricated by the Langmuir–Blodgett technique, possessing mainly a ferroelectric active phase and a controllable film thickness of 2.3 nm per layer. Atomic force microscopy and Fourier transform infrared spectroscopy were utilized to characterize the film properties. Importantly, the PVDF films could act as barrier layers to prepare spin transport devices using Fe3O4 and Co as bottom and top ferromagnetic electrodes, respectively. Spin-dependent electron transport behaviors were systemically studied in these devices by varying the PVDF film thickness from 3 layers (7 nm) to 13 layers (30 nm). With increasing PVDF layer numbers, the magnetoresistance (MR) response decreases likely due to the change in spin transport from tunneling to hopping transport. We further investigated the MR dependence on operation temperatures (150 K, 200 K, 250 K and 300 K). It is noteworthy that the MR effect was observed even at 300 K with an MR ratio exceeding 2.5%, which is achieved for the first time in such organic devices. The device performance could be further improved at lower operation temperatures. The MR ratios, device resistances and electron transport mechanisms in the present devices were also discussed to analyze the spin transport behaviors. The results indicate that the ferroelectric PVDF nanofilms are promising candidates for spin devices operated at room temperature, thereby shedding light on the design of organic ferroelectric spintronics with a higher performance.

Nanomagnetic CoPt truncated octahedral nanoparticles (TONPs) were successfully synthesised through a facile one-pot strategy. These single crystal CoPt TONPs with an average size of about 8 nm exhibit excellent electrocatalytic performance of both activity and stability for methanol oxidation reaction (MOR). The mass and specific activities of CoPt TONPs is 8 and 6 times higher than that of standard commercial Pt/C, respectively. After accelerated durability test (ADT), the loss of electrochemical surface area (ECSA) for CoPt TONPs is only 18.5%, which is significantly less than that of commercial Pt/C (68.2%), indicating that CoPt TONPs possess much better stability than commercial Pt/C in the prolonged operation. The Curie temperature of CoPt TONPs down to 8 nm is as high as 350 K with weak ferromagntism at room temperature (RT), which is greatly valuable for recycling in the eletrocatalytic applications.

Hexaferrites with noncollinear conical magnetic structures are among the most interesting and promising single-phase multiferroics. One puzzle remaining unsolved is why the spin-induced electric polarization can be either reversible or nonreversible by applying magnetic fields. We have unraveled a solution to this puzzle by a systematic study in the multiferroic hexaferrite ${\mathrm{Ba}}_{0.3}{\mathrm{Sr}}_{1.7}{\mathrm{Co}}_{2}{\mathrm{Fe}}_{11}{\mathrm{AlO}}_{22}$ where the electric polarization is reversible at low temperatures but nonreversible at high temperatures. Neutron diffraction results reveal that the rotation of spin cones with applied $ab$-plane magnetic field takes distinct paths at 150 and 305 K: in-plane and out-of-plane rotation, respectively. A theoretical analysis based on the spin current model confirms that the reversal of electric polarization is caused by the in-plane rotation. Our study clarifies the mechanism underlying the reversibility of spin-induced electric polarization in multiferroic hexaferrites.

Materials featuring negative thermal expansion (NTE) attract attention due to their numerous applications in printed circuit boards, machinery, optical-fiber reflective grating devices, and high-precision mirrors. Unfortunately, most large samples of NTE material are very sensitive to external magnetic fields. To address this stumbling block, the authors chemically modify CrAs, which can turn antiferromagnetic and thus field-insensitive, and obtain a large NTE coefficient across a large range that includes room temperature. Electrons in $3d$ orbitals are responsible for NTE, accompanied by a first-order antiferromagnetic-paramagnetic transition.

Magnetic refrigerant materials working at middle and low temperature range have drawn much attention because they can be used for gas liquefaction such as oxygen, nitrogen, hydrogen and helium. It is continuous goal for researchers to explore and obtain magnetic refrigerant materials with large magnetic entropy change, wide refrigerant temperature span, high refrigeration capacity and large adiabatic temperature change. RGa family is a kind of rare earth based intermetallic compounds with abundant magnetic transitions. This paper reviews the results of low-temperature order-order magnetic transition, high-temperature order-disorder magnetic transition and magnetic entropy change for PrGa, NdGa, SmGa, GdGa, TbGa, DyGa, HoGa, ErGa, TmGa and Er1− x Gd x Ga compounds. The low-temperature order-order magnetic transition includes spin reorientation transition, ferromagnetic to modulated antiferromagnetic transition and cone-ferromagnetic to cone-ferromagnetic transition. There are several peaks on the magnetic entropy change curves which provide ideas for designing magnetic refrigerant materials with large temperature span. The characteristics of magnetic transitions and magnetic entropy change for RGa compounds are analyzed, the dependency relationship together with related physical mechanism are expounded and the possible research interests in the future are discussed.

Flexible magnetic films have been widely investigated as a potential sensor to detect the stress or strain induced by bending. Nevertheless, the stable magnetic response is highly required in the case of wearable devices in which the bending-induced sensitivity variation should be minimized. Therefore, it is highly worthwhile to propose an approach to design a flexible magnetic film in need. Here, a flexible magnetic thin film of the potential spin gapless semiconductor CoFeMnSi (CFMS) is fabricated on an aluminum foil (Al foil), which is sensitive to the stress or strain induced under bending; but it was found that inserting a Ti3C2 MXene buffer layer, which acts as a sponge-like behavior, can significantly improve the magnetic response stability inert of the stress or strain. Impressively, the Hc can keep relatively constant under bending and the magnetic hysteresis loops remain unchanged even after repeated bending. Through the finite element calculation, we clarify the working mechanism of stress releasing by the buffer layer owing to the sponge-like elastic behavior. Our work proposes a novel approach to design flexible devices towards in need of tunable or endurable properties, and gives a theoretical instruction of selecting a buffer layer.

The binary alloy/ferromagnetic metal heterostructure has drawn extensive attention in the research field of spin–orbit torque (SOT) due to the potential enhancement of SOT efficiency via composition engineering. In this work, the magnetic properties and SOT efficiency in the Pt100 – x Ni x /Ni78Fe22 bilayers were investigated via the spin-torque ferromagnetic resonance (ST-FMR) technique. The effective magnetic anisotropy field and effective damping constant extracted by analyzing the ST-FMR spectra show a weak dependence on the Ni concentration. The effective spin-mixing conductance of 8.40 × 1014 Ω−1 ⋅ m−2 and the interfacial spin transparency T in of 0.59 were obtained for the sample of Pt70Ni30/NiFe bilayer. More interestingly, the SOT efficiency that is carefully extracted from the angular dependence of ST-FMR spectra shows a nonmonotonic dependence on the Ni concentration, which reaches the maximum at x = 18. The enhancement of the SOT efficiency by alloying the Ni with Pt shows potential in lowering the critical switching current. Moreover, alloying relatively cheaper Ni with Pt may promote to reduce the cost of SOT devices.

Polycrystalline monoclinic Er12Co7 compound with a large magnetocaloric effect (MCE) was synthesized. The maximum values of the magnetic entropy change (ΔSM) under the field changes of 0–2 T and 0–5 T reach 10.2 J/kgK and 18.3 J/kgK, respectively. In order to gain further insight in understanding the MCE, samples with various Ho substitutions for Er were fabricated and studied. It was found that Ho-substitution makes a great impact on the magnetic properties and MCE of Er12Co7 compound. Through compositional optimization, the mixed product of Ho12Co7 and Er6Ho6Co7 with the weight ratio of 58:42 was tailored to exhibit the best MCE performance. The maximum value of ΔSM, the full width at half maximum of ΔSM-T curve and the refrigerant capacity of the mixed compound are calculated to be 16.7 J/kgK, 37.9 K and 522 J/kg, respectively.

Fullerenes (C 60 and C 70 ) films have been fabricated by a thermal evaporation method. Raman spectra for C 60 and C 70 films were utilized to evaluate the film quality, and atomic force microscopy technique showed the roughness of both films was within the molecular scale of fullerenes. Moreover, these fullerenes (C 60 and C 70 ) films were successfully used to fabricate spin-valve devices with an Fe 3 O 4 /AlO/fullerenes (C 60 or C 70 )/Co/Al stacking structure to get an insight for spin conserved electron transport behaviors in C 60 and C 70 films. The magnetoresistance (MR) effects in these devices were investigated at both room and low temperatures. As reducing measurement temperature, the MR ratios increased in both fullerenes (C 60 and C 70 ) based devices due to the reduction of spin scattering. It is worth noting that the MR ratio in C 60 based devices is around one order of magnitude larger than that of C 70 based devices at room temperature. The dominant reason for the larger MR ratio in C 60 based spin valves compared to that in C 70 based devices is analyzed. This study may provide some criteria for organic semiconductors selection for designing spin based organic devices.

The high cost and poor durability of Pt nanoparticles (NPs) are great limits for the proton exchange membrane fuel cells (PEMFCs) from being scaled-up for commercial applications. Pt-based bimetallic NPs together with a uniform distribution can effectively reduce the usage of expensive Pt while increasing poison resistance of intermediates. In this work, a simple one-pot method was used to successfully synthesize ultrafine (about 7.5 nm) uniform NiPt truncated octahedral nanoparticles (TONPs) in dimethylformamid (DMF) without any seeds or templates. The as-prepared NiPt TONPs with Pt-rich surfaces exhibit greatly improved catalytic activities together with good tolerance and better stability for ethylene glycol oxidation reaction (EGOR) and oxygen reduction reaction (ORR) in comparison with NiPt NPs and commercial Pt/C catalysts in alkaline electrolyte. For example, the value of mass and specific activities for EGOR are 23.2 and 17.6 times higher comparing with those of commercial Pt/C, respectively. Our results demonstrate that the dramatic enhancement is mainly attributed to Pt-rich surface, larger specific surface area, together with coupling between Ni and Pt atoms. This developed method provides a promising pathway for simple preparation of highly efficient electrocatalysts for PEMFCs in the near future.

Hollow nanoparticles with large surface areas exhibit a lot of advantages for applications such as catalysis and energy storage. Furthermore, their performance can be manipulated by their deliberate assemblies. Dispersive hollow FePt nanospheres have been assembled into one-dimensional hollow FePt nanochains under the magnetic fields at room temperature. Based on the activation of galvanic replacement at different reaction stages, the size of hollow FePt nanochains can be deliberately manipulated varying from 20 nm to 300 nm, together with the length changing from 200 nm to 10 μm. The competition between movement of paramagnetic Fe(3+) ions and shape recovering due to thermal fluctuations plays a critical effect on the structure of contact area between hollow nanospheres, leading to perforative structures. Compared with commercial Pt/C, well aligned hollow FePt nanochains show greatly enhanced catalytic activities in the methanol oxidation reaction (MOR) due to more favorable mass flow. Magnetic measurements indicate that the magnetic properties including Curie temperature and saturation magnetization can be tuned by the control of the size and shape of hollow nanochains.

The promise of topologically vortex-like magnetic spin textures hinges on the intriguing physical properties and theories in fundamental research and their distinguished roles as high-efficiency information units in future spintronics. The exploration of such magnetic states with unique spin configurations has never ceased. In this study, the emergence of unconventional (anti)meron chains from a domain wall pair is directly observed at zero field in 2D ferromagnetic Fe5- x GeTe2 , closely correlated with significant enhancement of the in-plane magnetization and weak van der Waals interactions. The simultaneous appearance of a large topological Hall effect is observed at the same temperature range as that of the abnormal magnetic transition. Moreover, the distinctive features of the (anti)meron chains and their collective dynamic behavior under external fields may provide concrete experimental evidence for the recent theoretical prediction of the magnetic-domain-wall topology and endorse a broader range of possibilities for electronics, spintronics, condensed matter physics, etc.

The interfacial spin transmission and spin–orbit torques (SOTs) in as-grown and annealed W/Co2FeAl(CFA)/MgO multilayers are studied by the spin-torque ferromagnetic resonance (ST-FMR) technique. The effective spin-mixing conductance of 4.40 × 10 14 Ω − 1 m − 2 and the interfacial spin transparency Tin of 0.47 are obtained for the as-grown samples, which are comparable to those of the widely employed W/CoFeB bilayer. The annealing influence on the W/CFA/MgO multilayer is subsequently studied. The damping-like torque efficiency (ξDL) and field-like torque efficiency (ξFL) are extracted for different annealing temperatures via modulation of damping measurements and the angular dependence of ST-FMR spectra. Importantly, the ξDL value is fairly large (0.3 –0.5) and does not degrade even when the annealing temperature is increased up to 420 °C. Our results indicate that the studied W/CFA/MgO multilayers could be promising candidate materials for designing and developing SOT-driven spintronic devices.

Magnetic skyrmions are attracting interest as efficient information-storage devices with low energy consumption, and have been experimentally and theoretically investigated in multilayers including ferromagnets, ferrimagnets, and antiferromagnets. The 3D spin texture of skyrmions demonstrated in ferromagnetic multilayers provides a powerful pathway for understanding the stabilization of ferromagnetic skyrmions. However, the manipulation mechanism of skyrmions in antiferromagnets is still lacking. A Hall balance with a ferromagnet/insulating spacer/ferromagnet structure is considered to be a promising candidate to study skyrmions in synthetic antiferromagnets. Here, high-density Neel-type skyrmions are experimentally observed at zero field and room temperature by Lorentz transmission electron microscopy in a Hall balance (core structure [Co/Pt]n /NiO/[Co/Pt]n ) with interfacial canted magnetizations because of interlayer ferromagnetic/antiferromagnetic coupling between top and bottom [Co/Pt]n multilayers, where the Co layers in [Co/Pt]n are always ferromagnetically coupled. Micromagnetic simulations show that the generation and density of skyrmions are strongly dependent on interlayer exchange coupling (IEC) and easy-axis orientation. Direct experimental evidence of skyrmions in synthetic antiferromagnets is provided, suggesting that the proposed approach offers a promising alternative mechanism for room-temperature spintronics.

The effect of interfacial Pt layer on multi-resistance states in perpendicular Hall balance with core structure of [Co/Pt]n/NiO/[Co/Pt]n multilayers was systematically investigated. By inserting an ultrathin Pt layer between [Co/Pt]n and NiO spacer, resistance states and the Hall resistance ratio (HRR) were successfully tuned. Our results indicate that the inserted ultrathin Pt layer plays a crucial role on spin dependent transport properties, achieving a HRR of up to 30,900%. Furthermore, the resistance in Hall balance can be smoothly altered among 2-, 3-, and 4-states by optimizing the ultrathin active Pt layer. Pt catalyst with high electronic activity, as measured by X-ray photoelectron spectroscopy (XPS), provides a novel approach for modifying the interfacial orbital hybridization, thus leading to a tunable resistance states and HRR value.

The perpendicular magnetic anisotropy (PMA), current-induced spin–orbit torques (SOTs), and Dzyaloshinskii–Moriya interaction (DMI) in the as-grown W or Ta/Ir22Mn78(IrMn)/CoFeB/MgO stacks with varying IrMn layer thicknesses were investigated. The in-plane magnetized W/CoFeB/MgO sample becomes perpendicularly magnetized after inserting the IrMn layer without the requirement of the annealing process. The effective magnetization fields 4πMeff show a nonmonotonic dependence on the IrMn layer thickness, which reaches the maximum in magnitude at a thickness of tIrMn = 0.75 nm. The SOT effective fields corresponding to damping-like and field-like torques decrease with the insertion layer thickness. Moreover, the variation of the IrMn layer thickness leads to the change of the DMI in magnitude and sign change from positive (favoring right-handed chirality) to negative (favoring left-handed chirality). The realization of changing the PMA, SOTs, and DMI by inserting the IrMn layer provides more flexibility in the design of spintronic devices.

Pt-based one-dimensional hollow nanostructures are promising catalysts in fuel cells with excellent activity. Herein, one-dimensional hollow FePt nanochains were shown to be efficient nanocatalysts in the hydrolysis of NaBH4. The characterization of composition, structure and morphology identifies an ultrathin shell (∼3 nm) with uniformly distributed Fe30Pt70 constituents. The H2 generation rate of hollow Fe30Pt70 nanochains achieves 16.9 l/(min · g) at room temperature, while the activation energy is as low as 17.6 kJ mol-1 based on the fitting over the whole reaction time span. After the catalysis of NaBH4 hydrolysis, the morphology and composition of hollow FePt nanochains remain unchanged. Furthermore, the structural stability of hollow FePt nanochains under Ga+ ion irradiation is clarified. Theoretical simulation indicates that the stopping range of such a Fe30Pt70 shell is 7.7 keV, which offers a prediction that structure evolves diversely under Ga+ ions below and above such energy. The Ga+ ion irradiation experiments show a consistent trend with the simulation, where Ga+ ions with kinetic energy of 30 keV make the hollow architecture subside and sputter away, while Ga+ ions with kinetic energy of 5 keV only etch the top and lead to an eggshell structure.

Magnetic skyrmions in multilayers are particularly appealing as next generation memory devices due to their topological compact size, the robustness against external perturbations, the capability of electrical driving and detection, and the compatibility with the existing spintronic technologies. To date, N\'eel-type skyrmions at room temperature (RT) have been studied mostly in multilayers with easy-axis magnetic anisotropy. Here, we systematically broadened the evolution of magnetic skyrmions with sub-50-nm size in a series of Pt/Co/Ta multilayers where the magnetic anisotropy is tuned continuously from easy axis to easy plane by increasing the ferromagnetic Co layer thickness. The existence of nontrivial skyrmions is identified via the combination of in situ Lorentz transmission electron microscopy (L-TEM) and Hall transport measurements. A high density of magnetic skyrmions over a wide temperature range is observed in the multilayers with easy-plane anisotropy, which will stimulate further exploration for new materials and accelerate the development of skyrmion-based spintronic devices.

In general, ultrathin disordered FePt film exhibits in-plane magnetic anisotropy due to large demagnetization fields and negligible volume anisotropy. Here, we demonstrated that magnetization reorientation from in-plane to out-of-plane takes place when ultrathin disordered FePt film is sandwiched by amorphous SiO2 layers and annealed at 350 °C. Based on the interfacial and structural analysis from X-ray photoelectron spectroscopy and high resolution transmission electron microscopy, the reorientation originates from the electronic structural changes because of strong bonding between Fe and O atoms at the top FePt/SiO2 interface. This interface anisotropy plays a crucial role in the magnetic behaviour, resulting in magnetization reorientation of ultrathin disordered FePt film.

Au dendritic nanostructures with sharp tips have been successfully fabricated on a large scale by reducing potassium tetrachloroaurate (KAuCl4) with hydrofluoric acid on a Si wafer locally processed using a focused ion beam (FIB) technique. Surface enhanced Raman scattering (SERS) with Rhodamine B (RhB) molecules on a nanostructured substrate is greatly enhanced, originating from “hot-spots” located at the nanogaps between adjacent branches on dendritic nanostructures. Furthermore, Au dendritic nanostructures as recyclable SERS substrates exhibit an ultrasensitive response to the pico-scale concentration of probe molecules. This work shows that greatly enhanced SERS substrates with a high degree of reliability and reproducibility can be fabricated at a relatively low cost, which could help SERS to realize its full potential as a very sensitive tool for trace analysis.

The electronic structure, magnetism and phase stability of Ga2-based Heusler alloys Ga2MnCo and Ga2MnV are studied by first-principles calculations. The volume-conserving tetragonal distortions of the cubic Ga2MnCo and Ga2MnV show an energy minimum at c/a = 1.17 and 1.45, respectively. The isostructural alloying method is adopted to alloy two isostructures by substituting Co for V at density functional level. The calculations reveal that a potential tetragonal martensite phase can be expected with a large thermodynamic driving force and a moderate strain energy in Ga2MnCo–Ga2MnV system. For the middle composition of Ga2MnV0.5Co0.5, the energy difference between the martensite and parent phase reaches � 140 meV/cell and the degree of distortion arrives at c/a = 1.275, which corresponds to a potential martensitic transformation. Based on the calculated results, the exchange interaction between Mn and V atoms is found to change from antiferromagnetic to ferromagnetic coupling with increasing c/a.

A polycrystalline TmNiAl2 compound with transition temperature near the liquid helium boiling point was successfully synthesized. Magnetic measurements show that FM (ferromagnetic) to FM and FM to PM (paramagnetic) transitions take place at 2.4 K and 4.0 K, respectively. Magnetic entropy change (–ΔSM) is calculated, and its maximal value [(–ΔSM)max] reaches as high as 20.7 J/kg K with the field change of 0–5 T. The low transition temperature together with large (–ΔSM)max at the liquid helium temperature zone originates from the weak spin-spin exchange interaction between Tm atoms. For a clear comparison, the magnetocaloric effect (MCE) of polycrystalline RNiAl2 (R = Tb and Gd) samples was also prepared and investigated. For the TbNiAl2 compound, FIM (ferrimagnetic) to AFM (antiferromagnetic) and AFM to PM transitions occur at 11.0 K and 21.5 K, respectively. As for the GdNiAl2 compound, an FM to PM transition occurs at 30.5 K. The value of (–ΔSM)max under the field change of 0–5 T is calculated to be 11.8 J/kg K and 17.3 J/kg K for TbNiAl2 and GdNiAl2, respectively. Compared with other RNiAl2-series MCE materials, TmNiAl2 exhibits the lowest working temperature and relatively larger (–ΔSM)max. The large MCE at low temperature indicates that TmNiAl2 is competitive among the MCE materials working at a liquid helium temperature zone.A polycrystalline TmNiAl2 compound with transition temperature near the liquid helium boiling point was successfully synthesized. Magnetic measurements show that FM (ferromagnetic) to FM and FM to PM (paramagnetic) transitions take place at 2.4 K and 4.0 K, respectively. Magnetic entropy change (–ΔSM) is calculated, and its maximal value [(–ΔSM)max] reaches as high as 20.7 J/kg K with the field change of 0–5 T. The low transition temperature together with large (–ΔSM)max at the liquid helium temperature zone originates from the weak spin-spin exchange interaction between Tm atoms. For a clear comparison, the magnetocaloric effect (MCE) of polycrystalline RNiAl2 (R = Tb and Gd) samples was also prepared and investigated. For the TbNiAl2 compound, FIM (ferrimagnetic) to AFM (antiferromagnetic) and AFM to PM transitions occur at 11.0 K and 21.5 K, respectively. As for the GdNiAl2 compound, an FM to PM transition occurs at 30.5 K. The value of (–ΔSM)max under the field change of 0–5 T is calculated to be 11.8...

This study investigated the effect of geometrical parameters of gas coolers on system performance and the optimal discharge pressure with a developed and experimentally validated numerical model of an air-source transcritical CO 2 heat pump water heater system. This model fully considered actual heat transfer process in the gas cooler and characteristics of major components adopted in the prototype system. Simulation results showed a good agreement with experimental results in terms of heat yields, COP and the optimal discharge pressure. Parametric analysis reveals that a larger heat transfer area of the gas cooler increases heat yields but decreases the optimal discharge pressure while other components in the system remain unchanged. In addition, at the same operating condition with the same heat transfer area, heat yields increase with CO 2 mass fluxes by reducing tube diameters and flow passages of gas coolers, and beyond certain range of mass fluxes, the optimal discharge pressure increases sharply. As one result, the optimal range of CO 2 mass flux in heat exchange tubes should be the range of 155–325 kg m −2 s −1 at given condition in this paper.

Electric control of magnetism is demonstrated in a multiferroic metal-organic framework with a perovskite structure. A moderate electric field of a few kV/cm applied during the cooling process is able to cause a large (more than 50%) change of the magnetization at low temperature. This significant magnetoelectric effect is ascribed to the electric field manipulation of orientation of hydrogen bonds that modify the superexchange interaction between metal ions. [GRAPHICS] Electric-field cooling causes a large change in the magnetization of a multiferroic MOF. (c) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Transmission electron microscopy (TEM) is employed to characterize ex situ the interface between the bottom Fe (001) electrode and MgO (001) barrier in a magnetic tunnel junction (MTJ) deposited by molecular beam epitaxy. High resolution TEM images are compared with multislice-based simulations of oxidized and sharp interfaces to conclude that at least the part of the interface is not oxidized. In addition, the, spacing between the Fe and O layers at the interface is measured and found to be comparable with theoretical calculations in the literature of sharp interfaces. This result offers a methodology to characterize the interface structure of MTJs, which is important to determine the magneto-transport properties of the device.

A large enhancement of anomalous Hall sensitivity (S-v) by metal/oxide interfacial modification is obtained in a MgO/[Co/Pt](3)/MgO multilayered structure. The values of S-v are increased to 8363 V/A.T by CoO insertion and 2261 V/A.T by Pt insertion, while S-v is approximately 1000 V/A.T in normal Hall semiconductor sensors. Microstructural analysis shows that the crystal orientation of [Co/Pt](3) multilayers is improved, and the oxygen concentration is largely changed by introducing an ultrathin CoO layer at metal/oxide interfaces, leading to a large increment of S-v. (C) 2013 The Japan Society of Applied Physics

Synthesis and manipulation of advanced bimetallic nanomaterials via a green and low-cost wet chemical route are of great importance for the industrialization potential. Materials design integrating the synthesis of nanomaterials through an environmentally benign route with a simple manipulation method is a challenge. The CoPt hollow nanochains have been successfully synthesized in aqueous solution with shell thickness of about 5 nm and tunable length from 300 nm to 2 mu m. The as-prepared CoPt hollow nanochains can be easily aligned by the external magnetic fields and can be attached onto substrates, such as silicon wafer. The synthesis strategy is characterized by room temperature reaction (300 K), low cost, and utilization of facile reagents (water as solvent). Growth kinetics investigation shows the magnetostatic interactions between Co clusters together with the spontaneous galvanic replacement between Co clusters and Pt ions are indispensable for the formation of aligned hollow nanochains. Magnetic measurements indicate that the shape anisotrophy of 1D aligned nanochains plays a dominant role on the good controllable behavior.

Magnetic tunnel junctions (MTJs) with the core structure of CoFeB/MgAlOx/CoFeB were fabricated using magnetron sputtering technique. The MgAlOx tunnel barrier was obtained by plasma oxidation of an Mg/Al bilayer in an Ar+O2 atmosphere. Series of MTJs were fabricated with different Mg layer thicknesses (tMg), and Al layer thickness was fixed at 1.3 nm. The annealing effect on the tunneling magnetoresistance (TMR) ratio was investigated, and TMR ratio of 65% at room temperature (RT) was shown when it was annealed at 375 °C with the tMg=0.5 nm. The temperature dependence of conductance can be fit by the magnon-assisted tunneling model by adding spin independent tunneling contribution for the samples investigated here, and the spin independent conductance GSI varies with tMg, possibly due to less oxidation for thicker Mg layer.

Polypropylene (PP) films were grafted respectively with two different processes: air plasma graft (APG) and post-plasma grafting (PPG) using feather keratin. The graft results were compared by measuring contact angles, printability, ageing test and surface chemical composition analysis. The results showed that the surface hydrophilic and printing properties of the PP films after PPG were better than after APG. The contact angles went down from 34.7° to less than 10° and could sustain to 28° at the end of the test (30 days). The analyses of the C1s and N1s peaks by X-ray photoelectron spectroscopy (XPS) illustrated that polar groups, especially nitrogen-containing groups C–NHx and CO–NH, were introduced on the PP surface after PPG. The mechanisms of PPG were briefly discussed.

Topological zero-field nanometric domains and their capability to be manipulated by external fields show potential applications in spintronics. Here, the spontaneous magnetic bubbles (≈100 nm in diameter) are observed at zero field in a ferromagnetic manganite La1−xSrxMnO3 (0.15 < x

A stable plasma sheet with an area of 250 × 300 mm2 was generated between two different pairs of electrode models, a pair of hollow electrodes discharge model, a single hollow cathode, and a metal plate anode discharge model, by direct current discharge under an axial magnetic field. The electron density distribution across the sheet plasmas in the two different discharge models were compared by the measurements using Langmuir probe. The results showed that the electric field configuration of the pair of hollow electrodes discharge model was more effective to confine the electrons and showed higher electron density in the sheet plasma. The microwave return loss of the sheet plasma had been studied by using a microwave scale network analyzer and the sheet plasma exhibited almost the same reflection capability with an aluminum plate in a microwave range of 2.2 to 4 GHz, which indicated that the sheet plasma with high electron density could be used to reflect electromagnetic wave, and hopefully replace metal plate antenna.

The magnetic behavior and MCE property of NdGa compound were studied in detail. According to the temperature dependence of magnetization (M-T) curve at 0.01 T, two sharp changes were observed at 20 K (TSR) and 42 K (TC), respectively, corresponding to spin reorientation and FM-PM transition. Isothermal magnetization curves up to 5 T at different temperatures were measured and magnetic entropy change (ΔSM) was calculated based on M-H data. Temperature dependences of –ΔSM for a field change of 0-2 T and 0-5 T show that there are two peaks on the curves corresponding to TSR and TC, respectively. The value of the two peaks is 6.4 J/kg K and 15.5 J/kg K for the field change of 0-5 T. Since the two peaks are close, the value of –ΔSM in the temperature range between TSR and TC keeps a large value. The excellent MCE performance of NdGa compound benefits from the existence of two successive magnetic transitions.