Search

The combination of focused electron beam induced deposition (FEBID) and magnetic force microscopy (MFM) has opened up new possibilities in nanoscale magnetic imaging. FEBID offers precise control over the dimensions and magnetic properties of the MFM probes, enabling the development of high-performance magnetic tips with enhanced capabilities compared to conventional ones. These improved tips offer superior resolution, sensitivity, and versatility in nanoscale magnetic surface characterization. Here, we compare the performance of a commercial MFM tip and a FEBID-grown Fe tip in a Ni80Fe20/NdCo5 film. The FEBID tip exhibited superior lateral resolution for topography imaging, likely due to its sharper and well-defined geometry, with a tip diameter of approximately 20 nm. MFM measurements further confirmed this advantage, revealing better-defined magnetic domains and higher magnetic contrast with the FEBID-functionalized probes compared to the commercial tip. This improvement can be attributed to the possibility to optimize the tip-sample magnetic interaction for the FEBID tip. By reducing the lift height of the second pass, we were able to bring the tip closer to the sample, enhancing the magnetic signal without introducing significant topographic artifacts. Overall, these findings highlight the potential of FEBID for creating high-resolution and high-sensitivity MFM tips. [ABSTRACT FROM AUTHOR]

ABSTRACT Gold nanoparticles (AuNPs) of different sizes were synthesized into a crosslinked network of polyacrylamide (PAAm) microgels. PAAm was prepared by means of semicontinuous inverse heterophase polymerization under monomer-starving conditions with a z-average particle size of 384 ± 18 nm. AuNPs with controlled size were obtained by a reduction reaction of Au+3 to Au0 from a gold(III) chloride trihydrate (HAuCl4) solution inside microgel the crosslinked network (AuNP-PAAm). The reduction reaction was verified for 2 h by ultraviolet-visible spectroscopy (UV-vis). AuNP-PAAm exhibited a particle size between 288 ± 12 and 230 ± 15 nm at HAuCl4 concentrations of 0.4 and 1.3 m M, respectively. The AuNP-PAAms were observed by transmission electron microscopy, and their sizes were determined to be 19 ± 2 nm (1.3 m M) and 17 ± 2 nm (1.1 m M). With UV-vis spectroscopy, we detected the formation of AuNPs at a wavelength of 552 nm, and with X-ray diffraction analysis, we proved that the crystal arrangement was face-centered cubic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43560. [ABSTRACT FROM AUTHOR]

The synthesis of poly(N-isopropylacrylamide) nanogels by semi-continuous inverse heterophase polymerization (SIHP) under monomer starved conditions is reported here. This process consists in adding a N-isopropylacrylamide (NIPA) aqueous solution at a controlled rate over a monomer-free oleic solution containing surfactant and initiator. The nanogels became smaller with narrower size distributions as the addition rate was decreased. Moreover, nanogel sizes, the size distributions and more importantly, the polymer/surfactant ratios were smaller than those of PNIPA nanogels synthesized by batch inverse microemulsion polymerization (BIMP). The swelling behavior of these nanogels in water as a function of temperature is reported. As expected, all nanogels have a volume phase transition temperature at ca. 33–34°C. [ABSTRACT FROM PUBLISHER]

We give in this paper which is the third in a series of four a theory of covariant derivatives of representatives of multivector and extensor fields on an arbitrary open set U ⊂ M, based on the geometric and extensor calculus on an arbitrary smooth manifold M. This is done by introducing the notion of a connection extensor field γ defining a parallelism structure on U ⊂ M, which represents in a well-defined way the action on U of the restriction there of some given connection ∇ defined on M. Also we give a novel and intrinsic presentation (i.e. one that does not depend on a chosen orthonormal moving frame) of the torsion and curvature fields of Cartan's theory. Two kinds of Cartan's connection operator fields are identified, and both appear in the intrinsic Cartan's structure equations satisfied by the Cartan's torsion and curvature extensor fields. We introduce moreover a metrical extensor g in U corresponding to the restriction there of given metric tensor g defined on M and also introduce the concept of a geometric structure(U, γ ,g) for U ⊂ M and study metric compatibility of covariant derivatives induced by the connection extensor γ. This permits the presentation of the concept of gauge (deformed) derivatives which satisfy noticeable properties useful in differential geometry and geometrical theories of the gravitational field. Several derivatives of operators in metric and geometrical structures, like ordinary and covariant Hodge co-derivatives and some duality identities are exhibited. [ABSTRACT FROM AUTHOR]

Here (the last paper in a series of four) we end our presentation of the basics of a systematical approach to the differential geometry of a smooth manifold M (supporting a metric field g and a general connection ∇) which uses the geometric algebras of multivector and extensors (fields) developed in previous papers. The theory of the Riemann and Ricci fields of a triple (M, ∇, g) is investigated for each particular open set U ⊂ M through the introduction of a geometric structure on U, i.e. a triple (U, γ, g), where γ is a general connection field on U and g is a metric extensor field associated to g. The relation between geometrical structures related to gauge extensor fields is clarified. These geometries may be said to be deformations one of each other. Moreover, we study the important case of a class of deformed Levi–Civita geometrical structures and prove key theorems about them that are important in the formulation of geometric theories of the gravitational field. [ABSTRACT FROM AUTHOR]

This is the first paper in a series (of four) designed to show how to use geometric algebras of multivectors and extensors to a novel presentation of some topics of differential geometry which are important for a deeper understanding of geometrical theories of the gravitational field. In this first paper we introduce the key algebraic tools for the development of our program, namely the euclidean geometrical algebra of multivectors $\mathcal{C}\ell(V,G_{E})$ and the theory of its deformations leading to metric geometric algebras $\mathcal{C}\ell(V,G)$ and some special types of extensors. Those tools permit obtaining, the remarkable golden formula relating calculations in $\mathcal{C}\ell(V,G)$ with easier ones in $\mathcal{C}\ell(V,G_{E})$ (e.g. a noticeable relation between the Hodge star operators associated to G and GE). Several useful examples are worked in details for the purpose of transmitting the "tricks of the trade". [ABSTRACT FROM AUTHOR]

The main objective of this paper (second in a series of four) is to show how the Clifford and extensor algebras methods introduced in a previous paper of the series are indeed powerful tools for performing sophisticated calculations appearing in the study of the differential geometry of a n-dimensional manifold M of arbitrary topology, supporting a metric field g (of given signature (p,q)) and an arbitrary connection ∇. Specifically, we deal here with the theory of multivector and extensor fields on M. Our approach does not suffer the problems of earlier attempts which are restricted to vector manifolds. It is based on the existence of canonical algebraic structures over the canonical (vector) space associated to a local chart (Uo, ϕo) of a given atlas of M. The key concepts of a-directional ordinary derivatives of multivector and extensor fields are defined and their properties studied. Also, we recall the Lie algebra of smooth vector fields in our formalism, the concept of Hestenes derivatives and present some illustrative applications. [ABSTRACT FROM AUTHOR]