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Iron germanide (FeGe) emerges as a promising magnetic alloy for spintronics and high-density data storage, owing to its distinctive magnetic properties and compatibility with existing fabrication techniques. This compatibility enables the synthesis of customized FeGe nanocylinders characterized by chirality, where their magnetization asymmetrically twists. Within specific size parameters, these nanocylinders can accommodate skyrmions—swirling magnetic structures with significant implications for information storage and processing technologies. This study investigates the response of FeGe nanocylinders to external magnetic fields, focusing on how their magnetic properties vary with dimensions (diameter and length). Specifically, we analyze the impact of length on the pseudo-static properties of short FeGe nanocylinders and examine the average topological charge and remanence states across different aspect ratios. Our investigation underscores the relationship between chirality and diverse magnetization states in four types of nanocylinders with varying aspect ratios. This comprehensive analysis elucidates the connection between nanocylinder magnetic states and the average topological charge—a critical factor in advancing ultra-low-energy data storage and logic devices. [ABSTRACT FROM AUTHOR]

In this study, we investigate the pseudo-static magnetic properties of Permalloy conical frustum nanowires using micromagnetic simulations. We thoroughly examine how both the major and minor radii influence the magnetic reversal mechanism when an external magnetic field is applied parallel to the nanowire axis. The obtained results show that under specific geometrical conditions, magnetization reverts though a Bloch point-type domain wall. In these cases, hysteresis curves exhibit two Barkhausen jumps during magnetization reversal, forming a plateau field range in which a Bloch point domain wall nucleates and propagates until its annihilation after the second Barkhausen jump. The nucleation of a Bloch point domain wall in a frustum conical nanowire geometry is reported. These findings highlight the significance of this geometry in nucleating these attractive topological defects for promising applications. [ABSTRACT FROM AUTHOR]

In this work we performed a detailed numerical analysis to investigate the static and dynamic magnetic properties of hexagonal cells of square and circular cobalt nanodots as a function of the distance between them and the external magnetic field to which they are subjected. By simulating hysteresis curves with the external magnetic field applied parallel and perpendicular to the plane of these nanostructures, we can conclude that the cobalt nanodots presented a significant perpendicular magnetic anisotropy. We also obtained that the coercivity increases with decreasing volume, which implies that the circular dots have a higher coercivity than the square dots. Furthermore, we studied the dynamic susceptibility of these systems and found that it is possible to control both the position and the number of resonance peaks by controlling the geometry and the distance between the magnetic nanodots. This work provides useful information on the behaviour of cobalt nanodot arrays, opening paths for the design and improvement of two-dimensional technological devices. [ABSTRACT FROM AUTHOR]

In this work we performed a detailed numerical analysis to investigate the dynamic susceptibility of 1000 nm long Fe3O4 nanotubes by varying the diameter, the tube wall thickness and the magnitude of the external magnetic field applied along the tube axis. We found two well-defined modes, one of low frequency associated with the caps of the nanotubes, and another of high frequency associated with the central area of the nanotubes, which can be controlled by varying the geometry of the tubes or the external magnetic field to which they are subjected. These results allow us to suggest the use of these nanotubes in applications that require controlling the resonant frequency in the GHz range. [ABSTRACT FROM AUTHOR]

Films comprising predominantly novel isomers of C60 [=C60(nIPR)] have been generated by low energy ion beam deposition of vibronically excited C60+ onto graphite followed by selective sublimation of C60(Ih) from the deposited isomer mixture. The incident ions were generated by electron impact ionization/fragmentation of sublimed C70. Images of the C60(nIPR) films obtained by applying atomic force microscopy show aggregates, which we attribute to covalently interlinked C60(nIPR) units. The covalent bonds are inferred from the significantly higher thermal stability of the C60(nIPR) films compared to the C60(Ih) van der Waals solid–as measured by thermal desorption with mass spectrometric detection of the C60 mass channel (the only desorbable species). In contrast to the characteristic doublet structure of the occupied valence band in the ultraviolet photoelectron spectrum of pure C60(Ih), the valence band of C60(nIPR) films exhibits a triplet feature with the additional peak occurring at a binding energy of ∼2.6 eV. This is an indicator of the electronic modifications induced by intermolecular bonding. C60(nIPR) films exhibit a narrower band gap than found for C60(Ih). They also have significantly different chemical reactivity toward incorporation of thermal energy deuterium atoms. In order to model the experimental photoelectron spectra, various covalently linked oligomers of #1809C60(C2v), the second most stable conventional 60-atom fullerene cage, were calculated by means of the density functional theory. These spectral predictions together with analogous previous observations on related fullerene solids such as C58 lead us to infer that C60(nIPR) films consist of fullerene cage isomers containing one or more adjacent pentagon pairs, which mediate covalent cage-cage interconnection. [ABSTRACT FROM AUTHOR]

Disorder was induced in pristine highly oriented pyrolytic graphite (HOPG) by irradiation with H + ions with energies of 0.4 MeV and 1 MeV, and doses of 10 14 ions/cm 2 and 10 16 ions/cm 2 . Raman spectroscopy was used as the main technique to characterize different samples and gain new insights on the splitting of the D band into two components (D 1 and D 2 ), trying to correlate this feature of the vibrational spectrum with the impinging energy and dose. An increased I D2 / I G ratio in comparison with I D1 / I G was observed in the irradiated samples. This behavior indicates that the impinging energy mainly affects the D 1 component, while the D 2 component is strongly dominated by the dose. We expect a larger contribution of defects (originating from the rupture of C-C sp 2 symmetry through the formation of C-H sp 3 bonds) to the D 2 component than to the D 1 component. SQUID measurements of the irradiated samples showed an enhancement in the normalized remanence, as well as an increment in coercivity compared to pristine HOPG, consistent with H + -induced point-like defects as well as C-H bonds. AFM scanning after Raman and SQUID characterization showed a distribution of surface defects, which were ascribed to the burst of hydrogen blisters formed as a consequence of the irradiation process. The results presented in this work contribute to the current trend in nanotechnology in areas devoted to the control of properties by defect engineering in carbon-based materials.