Ferromagnetic,Folded Electrode Composite as a Soft Interface to the Skin for Long‐Term Electrophysiological Recording

A class of ferromagnetic, folded, soft composite material for skin‐interfaced electrodes with releasable interfaces to stretchable, wireless electronic measurement systems is introduced. These electrodes establish intimate, adhesive contacts to the skin, in dimensionally stable formats compatible with multiple days of continuous operation, with several key advantages over conventional hydrogel‐based alternatives. The reported studies focus on aspects ranging from ferromagnetic and mechanical behavior of the materials systems, to electrical properties associated with their skin interface, to system‐level integration for advanced electrophysiological monitoring applications. The work combines experimental measurement and theoretical modeling to establish the key design considerations. These concepts have potential uses across a diverse set of skin‐integrated electronic technologies.     

Modulation of magnetoelectric coupling through systematically engineered spin canting in nickel–zinc ferrite

A nickel–zinc ferrite system, which is one of the well-known versatile soft-ferromagnetic oxides, was investigated in terms of magnetoelectric (ME) coupling at room temperature. Herein, we demonstrated that spin canting is manipulated through a composition-induced structural transition from an inverse to a normal spinel structure, leading to modulation in the ME coupling. The ME coefficient was maximized at 60 at.% Zn substitution with a value of 0.1 mV/(Oe·cm), denoting ∼70% enhancement compared to that of the pure nickel ferrite. It was revealed that the interspin angle is enhanced along the octahedral site at up to ∼60 at.% Zn substitution, consistent with the composition level at the culmination of the ME coupling, evidenced by X-ray diffraction profiles and magnetic hysteresis loops combined with density functional theory calculations. Given that this approach is based on a tractable fabrication method, this study is expected to be widely used in modulation of the ME coupling in spinel-structured oxides.     

La_(0.67)Sr_(0.33-x)Ag_(x-y□y)MnO_3/Ag_y多晶材料的磁电阻

采用溶胶-凝胶(sol-gel)法制备La0.67Sr0.33-xAgx-y□yMnO3/Agy(x=0.20,0.30)多晶粉末,经压制与1 400℃/12h烧结获得相应的块体材料,借助X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)和多功能物性测量系统(PPMS,附件VSM),对材料的相结构、微观结构和磁性能进行研究。结果表明:La0.67Sr0.33-xAgx-y□yMnO3/Agy粉末形貌为接近球形的凸多面体,平均粒度在150 nm左右,块体材料结构致密但粒度变大。另外,粉末与块体材料中都有金属Ag相和Sr空位存在。在室温下块体材料的磁电阻较小,而且为负值。在低温区,外加磁场越高,则磁电阻越大,在外加磁场为3T、温度为174和20 K条件下,La0.67Sr0.13Ag0.20-y□yMnO3/Agy的磁电阻分别为-37.5%和-43.3%,在141和20 K温度下La0.67Sr0.03Ag0.30-y□yMnO3/Agy的磁电阻分别为-45.1%和-53.9%。     

低能离子束方法制备磁性Fe-Si合金薄膜

利用质量分离的低能离子束技术．获得了磁性Fe-Si合金薄膜。利用俄歇电子能谱法(AES)、X射线衍射法(XRD)以及交变梯度样品磁强计(AGM)测试了样品的组分、结构以及磁特性。测试结果表明在室温下制备的Fe-Si合金是Fe组分渐变的非晶薄膜,具有室温铁磁性。当衬底温度为300℃时制备的非晶Fe-Si薄膜中有Fe硅化物FeSi相产生．样品的铁磁性被抑制。     

Tunable optical,electronic and magnetic properties of semiconductor nanoparticles induced by magnetic and nonmagnetic dopants: A comparative experimental and theoretical study

While combining semiconductor and magnetic properties at the nanoscale provides dilute magnetic semiconductor (DMS) nanomaterials with a wide range of applications in next-generation electronic devices, tuning DMS properties still presents a challenge. Here, the synthesis of pure ZnO and transition metal (TM)-doped ZnO nanoparticles (NPs) with different magnetic (Fe and Co) and nonmagnetic (Mn) dopant concentrations (ranging from 2% to 10%) is reported using a co-precipitation method. Introducing the TM-dopants into ZnO NPs with 35?nm wurtzite structure causes crystallite and mean NP sizes to decrease, as characterized by X-ray diffraction and field-emission scanning electron microscopic analyses. Room-temperature magnetic measurements indicate coexistence of paramagnetic and ferromagnetic phases with tunability in the resulting TM-doped NPs. The maximum ferromagnetic coercivity and saturation magnetization are found to be 89?Oe and 0.074?emu/g for 10% Fe-doped ZnO NPs. UV–visible spectra showed a blue shift with increasing the dopant concentration, being in agreement with increasing trend in band gap energy calculated from band structure and density of state of TM-doped ZnO nanocrystal systems.     

二维Fe5GeTe2单晶的大量制备及吸波性能研究

目的 快速制备克量级、高质量的二维磁性Fe₅GeTe₂单晶,并开发具有范德华结构、室温铁磁性及优异微波吸收性能的新型吸波材料。方法 通过调控输运剂的含量,并缩短化学气相传输法的恒温段时长,以探索高质量Fe₅GeTe₂单晶的快速、制备量大的方法。将Fe₅GeTe₂单晶与石蜡按不同质量分数混合后,通过同轴线测试法分析其微波性能。结果 成功制备了克量级、高质量的Fe₅GeTe₂单晶样品。借助矢量分析仪的同轴线测试法研究Fe₅GeTe₂单晶的微波损耗性能发现,当Fe₅GeTe₂的质量分数为30%时,Fe₅GeTe₂的吸波特性较差,最佳反射损耗值仅为-4.8dB;当Fe₅GeTe₂的质量分数达到70%时,Fe₅GeTe_...     

Glycine-nitrate auto-combustion synthesis and magnetic properties of nanocrystalline NdAlxFe1-xO3 perovskites

The effect of substitution of Fe³⁺ by Al³⁺ on the structure and magnetic properties of NdAl_xFe_1-xO₃ perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was studied.All samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples ...     

High Curie Temperature Ferromagnetism and High Hole Mobility in Tensile Strained Mn‐Doped SiGe Thin Films

Diluted magnetic semiconductors based on group‐IV materials are desirable for spintronic devices compatible with current silicon technology. In this work, amorphous Mn‐doped SiGe thin films are first fabricated on Ge substrates by radio frequency magnetron sputtering and then crystallized by rapid thermal annealing (RTA). After the RTA, the samples become ferromagnetic semiconductors, in which the Curie temperature increases with increasing Mn doping concentration and reaches 280 K with 5% Mn concentration. The data suggest that the ferromagnetism comes from the hole‐mediated process and is enhanced by the tensile strain in the SiGe crystals. Meanwhile, the Hall effect measurement up to 33 T to eliminate the influence of anomalous Hall effect reveals that the hole mobility of the annealed samples is greatly enhanced and the maximal value is ≈1000 cm² V^?1 s^?1, owing to the tensile strain‐induced band structure modulation. The Mn‐doped SiGe thin films with high Curie temperature ferromagnetism and high hole mobility may provide a promising platform for semiconductor spintronics.     

Room-temperature ferromagnetic organic magnets derived from fluoro-graphite via facile halide exchange

Room-temperature ferromagnetic organic magnet is developed via a facile halide exchange process using fluoro-graphite (FG) as a starting material. Structural and chemical analysis reveals that heterogeneous C–F bond cleavage in the defect sites of FG is essentially related to the formation of ferromagnetic hydroxyl-graphene (HG). Pyrolysis of FG in a polar solvent with iodine ions induces a formation of metastable C–I bond and subsequent replacement of the I sites with the hydroxyl groups. Specifically, defective sites can be formed in FG due to nucleophile attack where the OH groups can be easily generated. As a result, the FG can be transformed into the HG with a network of sp²-conjugated carbon motifs in a sp³-based graphene matrix. Hence, the paramagnetic centers in the π-electron system of FG can be transformed to the long-range ordered ferromagnetic centers in the sp²-conjugated system of HG. Electron paramagnetic resonance data demonstrate the weak ferromagnetic property of HG stable at room temperature.     

Self‐Assembled Platinum Nanochain Networks Driven by Induced Magnetic Dipoles

Developing a reliable technique to organize nanoscale building blocks into ordered one‐dimensional assemblies is of particular interest in a range of practical applications. Here, for the first time, it is reported that platinum (Pt) nanoparticle chain networks can be assembled spontaneously in solution on a large scale. The in‐situ induced magnetic dipoles are believed to be the driving force for producing such elegant assembled nanochains. The alterant electronic structure of Pt modified by a very thin layer of polyvinylpyrrolidone (PVP) molecules leads to the ferromagnetism of Pt (a traditional paramagnetic metal), which has been verified by a series of analysis techniques and theoretical modeling. The temperature‐ and time‐dependent nucleation, growth, and organization processes of Pt chain networks are carefully investigated. These findings not only present the uncommon ferromagnetism of Pt, but also raise a possibility for expanding this strategy towards other assemblies of nonmagnetic nanoscale building blocks.