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  1. Free, publicly-accessible full text available November 1, 2023
  2. Silicon is an extremely important technological material, but the current industrial production of silicon by carbothermic reduction of SiO₂ is energy intensive and generates CO₂ emission. Here we developed a new and more sustainable method to produce silicon nanowires in bulk quantities via direct electrochemical reduction of CaSiO₃, an abundant and inexpensive silicon source soluble in molten salts, at a low temperature of 650 ⁰C by using low melting point ternary molten salts CaCl₂-MgCl₂-NaCl, which still retains high CaSiO₃ solubility, and a supporting electrolyte of CaO, which facilitates the transport of O²¯ anions, drastically improves the reaction kinetics and enables the electrolysis at low temperatures. The Si nanowire product can be used as high-capacity Li-ion battery anode materials with excellent cycling performance. This practical strategy at lower temperatures can be applied to other molten salt systems and also promising for waste glass and coal ash recycling. 
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  3. Abstract

    In bulk chiral crystals, 3D structures of magnetic skyrmions form topologically protected skyrmion strings (SkS) that have shown potential as magnonic nano‐waveguides for information transfer. Although SkS stability is expected to be enhanced in nanostructures of skyrmion‐hosting materials, experimental observation and detection of SkS in nanostructures under an applied in‐plane magnetic field is difficult. Here, temperature‐dependent magnetic field‐driven creation and annihilation of SkS in B20 FeGe nanostructures (nanowires and nanoplates) under in‐plane magnetic field (H||) are shown and the mechanisms behind these transformations are explained. Unusual asymmetric and hysteretic magnetoresistance (MR) features are observed but previously unexplained during magnetic phase transitions within the SkS stability regime whenH||is along the nanostructure's long edge, which increase the sensitivity of MR detection. Lorentz transmission electron microscopy of the SkS and other magnetic textures underH||in corroboration with the analysis of the anisotropic MR responses elucidates the field‐driven creation and annihilation processes of SkS responsible for such hysteretic MR features and reveals an unexplored stability regime in nanostructures.

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  4. Abstract

    Magnetic skyrmions are topologically protected spin textures that are being investigated for their potential use in next generation magnetic storage devices. Here, magnetic skyrmions and other magnetic phases in Fe1−xCoxGe (x< 0.1) microplates (MPLs) newly synthesized via chemical vapor deposition are studied using both magnetic imaging and transport measurements. Lorentz transmission electron microscopy reveals a stabilized magnetic skyrmion phase near room temperature (≈280 K) and a quenched metastable skyrmion lattice via field cooling. Magnetoresistance (MR) measurements in three different configurations reveal a unique anomalous MR signal at temperatures below 200 K and two distinct field dependent magnetic transitions. The topological Hall effect (THE), known as the electronic signature of magnetic skyrmion phase, is detected for the first time in a Fe1−xCoxGe nanostructure, with a large and positive peak THE resistivity of ≈32 nΩ cm at 260 K. This large magnitude is attributed to both nanostructuring and decreased carrier concentrations due to Co alloying of the Fe1−xCoxGe MPL. A consistent magnetic phase diagram summarized from both the magnetic imaging and transport measurements shows that the magnetic skyrmions are stabilized in Fe1−xCoxGe MPLs compared to bulk materials. This study lays the foundation for future skyrmion‐based nanodevices in information storage technologies.

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