Spin-dependent tunnelling in magnetite nanoparticles

Williams, G. V. M.; Prakash, T. L.; Kennedy, J.; Chong, Shen V.; Rubanov, S.

doi:10.1016/j.jmmm.2018.04.017

Cited by 101 publications

(21 citation statements)

References 30 publications

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“…It is comparable to that reported for ∼2.7 nm diameter Ni 1-x Fe x nanoparticles with x = 0.47 and made by dual ion beam implantation where m f .u.,sat = 1.0 µ B (Williams et al, 2019). Nanoscale magnetic materials typically have lower m f .u.,sat than the bulk (Vitta et al, 2008;Demortière et al, 2011;Upadhyay et al, 2016;Williams et al, 2018).…”

Section: Results and Analysismentioning

confidence: 95%

“…It is also possible that they can have nanodomains extending across the diameter of the fiber and hence they could be used for nanoscale domain wall magnetic memory (Cisternas et al, 2017). Metallic and ferromagnetic nanofibers that display a degree of electronic spin polarization could also potentially be used in spin-tunneling junctions (Katti, 2002;Parkin et al, 2004;Williams et al, 2018) for magnetic RAM applications where their small size could lead to high density storage as well as lower power when compared with multilayer thin films. They could also be used for spin-tunneling nano-magnetic sensors where the long lengths in relation to the diameter can ensure flux guiding along the length of the fiber and hence magnetic sensing directionality provided that the magnetic permeability is high enough.…”

Section: Introductionmentioning

confidence: 99%

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Electrospun, Oriented, Ferromagnetic Ni1-xFex Nanofibers

et al. 2020

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Electrospinning has been used to fabricate ferromagnetic Ni 0. 47Fe 0.53 nanofiber mats that were composed of individual, orientated Ni 0.47 Fe 0.53 nanofibers. The key steps were processing a polyvinylpyrrolidone nanofiber template containing ferric nitrate and nickel acetate metal precursors in Ar at 300 • C and then 95% Ar: 5% H 2 at 600 • C. The Ni 0.47 Fe 0.53 fibers were nanostructured and contained Ni 0.47 Fe 0.53 nanocrystals with average diameters of ∼14 nm. The Ni 0.47 Fe 0.53 ferromagnetic mats had a high saturation magnetic moment per formula unit that was comparable to those reported in other studies of nanostructured Ni 1-x Fe x. There is a small spin-disordered fraction that is typically seen in nanoscale ferromagnets and is likely to be caused by the surface of the nanofibers. There was an additional magnetic contribution that could possibly stem from a small Fe 1-z Ni z O phase fraction surrounding the fibers. The coercivity was found to be enhanced when compared with the bulk material.

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Section: Results and Analysismentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Electrospun, Oriented, Ferromagnetic Ni1-xFex Nanofibers

et al. 2020

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“…The temperature and pH for the optimal activity of the enzyme are 80-90 °C and 5.5-7.0. preparation of the fe 3 o 4 magnetic nanoparticles. The Fe 3 O 4 nanoparticles were prepared by a coprecipitation method 47,48 . In a typical process, 1.7 g FeCl 3 •6H 2 O and 0.66 g FeCl 2 •4H 2 O (the molar ratio of the two materials was 2:1) were placed in a 250 ml 3-neck flask, and 20 ml deionized water was added to the flask.…”

Section: Methodsmentioning

confidence: 99%

Reduction of nitroarenes by magnetically recoverable nitroreductase immobilized on Fe3O4 nanoparticles

Zhang

Liu

et al. 2020

Sci Rep

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Enzymes as catalysts have attracted significant attention due to their excellent specificity and incomparable efficiency, but their practical application is limited because these catalysts are difficult to separate and recover. A magnetically recoverable biocatalyst has been effectively prepared through the immobilization of a nitroreductase (oxygen-insensitive, purified from Enterobacter cloacae) onto the fe 3 o 4 nanoparticles. the magnetic nanoparticles (Mnps) were synthesized by a coprecipitation method in an aqueous system. The surfaces of the MNPs were modified with sodium silicate and chloroacetic acid (CAA). Using 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) through a covalent binding, nitroreductase was loaded onto the modified magnetic carriers through covalent coupling, and thus, a magnetically recoverable biocatalyst was prepared. The free and immobilized nitroreductase activity was also investigated by the reduction of p-nitrobenzonitrile using nicotinamide adenine dinucleotide phosphate (NAPDH) as a cofactor. The activity of the immobilized enzyme was able to maintain 83.23% of that of the free enzyme. The prepared enzyme can easily reduce substituted nitrobenzene to substituted aniline at room temperature and atmospheric pressure, and the yield is up to 60.9%. Most importantly, the loaded nitroreductase carriers can be easily separated and recycled from the reaction system using an externally applied magnetic field. The magnetically recoverable biocatalyst can be recycled and reused 7 times while maintaining high activities and the activity of the magnetic catalyst can be maintained at more than 85.0% of that of the previous cycle. This research solves the recovery problem encountered in industrial applications of biocatalysts and presents a clean and green method of preparing substituted aniline.Biocatalysis is an important green and sustainable technology, because it is an ideal approach that can be used to meet the challenges of energy conservation and environmental sustainability 1,2 . Enzymes, which are natural biocatalysts, are becoming more and more important in industrial applications, because enzymes can be used at pH values, temperatures and pressures that are moderate, and enzymes form few byproducts and have high activities and an unparalleled selectivity 3-5 . However, there are two challenges that need to be addressed in practical applications. One of the challenges is that enzymes can be denatured, i.e., the native three-dimensional structure unfolds, and this occurs as a result of exposure of the enzyme to solvents or changes in the temperature and pH. Another challenge is that enzyme reuse is often hardly feasible. The recovery and reuse of enzymes is also a decisive factor in the production cost 6 .Specifically, enzymes lack long term stability under processing conditions, and it is very difficult to recover the enzyme from the reaction system. Most heterogeneous systems require either a filtration or centrifugation step or tedious processing of the final react...

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“…This was due to the formation of Nd 2 Fe 14 B nanoparticles on the surface and their subsequent removal, leaving behind the defects. The HRTEM image of the selected area (1) shows that the area contained elemental a-Fe particles with a crystal plane spacing of 0.202 nm, which can be assigned to the (110) lattice plane of a-Fe, Fig. 8(B).…”

Section: Characteristics Of Nd-fe-b Powders Obtained By Reduction-difmentioning

confidence: 99%

“…In recent years, synthesis of magnetic nanostructures has been investigated for various permanent magnet (PM) applications due to their unique structural, electrical and magnetic properties. [1][2][3][4] PMs are widely used in modern energy conversion devices, such as electric vehicles, wind turbine generators, information storage, energy conversion systems, etc. [5][6][7][8][9][10] In particular, the Nd-Fe-B based PMs present the best magnetic properties, which can make these devices and systems smaller, lighter and more energy efficient.…”

Section: Introductionmentioning

confidence: 99%