Ribbon Axis Research Articles

Magnetic properties and structure of short-term annealed FeCuBPSi nanocrystalline alloys

Alloys with composition Fe80−xCu1B11P4Si4+x (x = 0 and 4), i. e. with Si 4 at % or 8 at % have been prepared by rapid quenching from the melt in air. For comparison the alloy with P 3 at % and Si 8 at % has been investigated as well. As-quenched structure of all ribbons was checked by X-ray diffraction. Subsequently the samples were submitted to thermal analysis, scanning and transmission electron microscopy and magnetic measurements. Hysteresis loops of strips after short-term annealing at 400, 420 and 500 °C for 5 min changed their shape – the saturation magnetic polarization increased. Its value changed from 1.67 to 1.74 T depending of the crystalline volume fraction for Fe80Cu1B11P4Si4 alloy. Addition of Si to the studied P 4 at % alloy leads to a decrease of coercivity after short-term annealing at the temperatures below the onset of the first transformation. Magnetic work decreased several times and its orientation acquired the distinct orientation along the ribbon axis.

On-Surface Synthesis of Edge-Extended Zigzag Graphene Nanoribbons.

Graphene nanoribbons (GNRs) have gained significant attention in nanoelectronics due to their potential for precise tuning of electronic properties through variations in edge structure and ribbon width. However, the synthesis of GNRs with highly sought-after zigzag edges (ZGNRs), critical for spintronics and quantum information technologies, remains challenging. In this study, a design motif for synthesizing a novel class of GNRs termed edge-extended ZGNRs is presented. This motif enables the controlled incorporation of edge extensions along the zigzag edges at regular intervals. The synthesis of a specific GNR instance-a 3-zigzag-rows-wide ZGNR-with bisanthene units fused to the zigzag edges on alternating sides of the ribbon axis is successfully demonstrated. The resulting edge-extended 3-ZGNR is comprehensively characterized for its chemical structure and electronic properties using scanning probe techniques, complemented by density functional theory calculations. The design motif showcased here opens up new possibilities for synthesizing a diverse range of edge-extended ZGNRs, expanding the structural landscape of GNRs and facilitating the exploration of their structure-dependent electronic properties.

Correlation between stress relaxation induced anisotropy, magnetic domain, and permeability of Co-doped FeCuSiBNbMn alloys

The effect of Co contents on the permeability, magnetic anisotropy, and structure has been investigated for FeSiBNbCuMn amorphous alloys during annealing with and without tensile stress. Large stress relaxation-induced anisotropy (Ku) of 482.0–1485.4 J/m3 is observed with an easy axis perpendicular to the direction of tensile stress (i.e., ribbon axis), which results in constant permeability of 1–2.8 × 103 at 1 kHz − 1 MHz. Different from the irregular domain structure in the samples annealed without tensile stress, stress annealing generates regular domains and 180° straight walls, and domain width increases with the increases of Co contents. Besides, the correlation between permeability, induced anisotropy, and domain width is established. These results could provide a good guide for improving the frequency stability of permeability by adjusting anisotropy and domain structure.

Nonuniformity of magnetization processes of a cobalt-based amorphous alloys in the as-quenched state

The magnetization processes nonuniformity of an amorphous cobalt-based soft-magnetic alloy AMAG-172 (Co-Ni-Fe-Cr-Mn-Si-B) in the as-quenched state were studied. Studies have shown that the main reason of the magnetic characteristics and magnetization processes nonuniformity is the nonuniformity of internal stresses due to the alloy manufacture method. An indirect characteristic of internal stresses is the domains volume with orthogonal magnetization. The observed bimodal field dependence of the magnetic permeability and the field shift of the hysteresis loops in the region of 180-degree domain walls displacement are a consequence of the nonuniformity of the alloy over its thickness. The field shift and the asymmetry of hysteresis loops are explained in terms of the formation of a unidirectional exchange anisotropy at the interface between the ferromagnetic and antiferromagnetic phases of the planar magnetization components oriented along the ribbon axis. The field shift disappearance and the asymmetry of the hysteresis loops along the width of the tape can be interpreted as a decrease in the thickness of the CoO oxide antiferromagnetic layer due to the difference in the concentrations and depth of oxygen and hydrogen atoms penetration induced into the surface of the tape during the manufacture of the tape as a result of interaction with atmospheric vapor.

Tailoring Magnetic Properties and Magnetoimpedance Response in Nanocrystalline (Fe3Ni)81Nb7B12 Ribbons for Sensor Applications

Today, there is an increasing demand for progress in the magnetoimpedance (MI) response of cost-effective soft-magnetic materials for use in high-performance sensing devices. In view of this, we investigate here the field-annealing effects on soft-magnetic properties, magnetoimpedance response, and field sensitivity in the nanocrystalline (Fe3Ni)81Nb7B12 alloy ribbons. We observe that within the low-frequency regime, between 2 and 5 MHz, the zero-field-annealed (ZFA) ribbons exhibit the highest magnetoimpedance values. By magneto-optical Kerr effect measurements, we show that this result stems from the formation of irregular transversally patched magnetic domains after annealing, which in turn explains the induced transverse anisotropy necessary to increase the GMI response. In addition, we discuss this increment in terms of skin effect. Moreover, we report that the highest sensitivity of ca. 189%/(kA/m)—15%/Oe—is achieved for the field-annealed samples whose magnetic field was applied transverse to the ribbon axis. These findings are of practical importance to develop and refine highly sensitive magnetic sensors.

Decoupling 1D and 2D features of 2D sp-nanoribbons—the megatom model

The dependence of the electron energy band gap on the width of an sp-nanoribbon is investigated using a generalization of the 1D tight binding model for a chain of atoms. Within the proposed generalization, small linear atomic formations along lines perpendicular to the 2D ribbon axis are modeled as single large atoms called megatoms whose properties depend on the type, the size and the atomic conformation. Replacement of a 1D chain of atoms by that of the megatoms is accompanied by the incorporation of zeroth order 2D features into the 1D model approximation of the nanoribbon. We use this model to investigate the oscillating band gap of an sp-nanoribbon in terms of the ribbon’s width. Results are presented for the width dependence of the energy gap of the zig-zag Si2BN nanoribbons.

Multiphoton absorption and Rabi oscillations in armchair graphene nanoribbons

We present an analytical approach to the problem of the multiphoton absorption and Rabi oscillations in an armchair graphene nanoribbon (AGNR) in the presence of a time-oscillating strong electric field induced by a light wave directed parallel to the ribbon axis. The two-dimensional Dirac equation for the massless electron subject to the ribbon confinement is employed. In the resonant approximation the electron-hole pair production rate, associated with the electron transitions between the valence and conduction size-quantized subbands, the corresponding multiphoton absorption coefficient and the frequency of the Rabi oscillations are obtained in an explicit form. We trace the dependencies of the above quantities on the ribbon width and electric field strength for both the multiphoton assisted and tunneling regimes relevant to the time-oscillating and practically constant electric field, respectively. A significant enhancement effect of the oscillating character of the electric field on the intersubband transitions is encountered. Our analytical results are in qualitative agreement with those obtained for the graphene layer by numerical methods. Estimates of the expected experimental values for the typically employed AGNR and laser parameters show that both the Rabi oscillations and multiphoton absorption are accessible in the laboratory. The data relevant to the intersubband tunneling makes the AGNR a 1D condensed matter analog in which the quantum electrodynamic vacuum decay can be detected by applying an external laboratory electric field.

Free-standing large, ultrathin germanium selenide van der Waals ribbons by combined vapor-liquid-solid growth and edge attachment.

Among group IV monochalcogenides, layered GeSe is of interest for its anisotropic properties, 1.3 eV direct band gap, ferroelectricity, high mobility, and excellent environmental stability. Electronic, optoelectronic and photovoltaic applications depend on the development of synthesis approaches that yield large quantities of crystalline flakes with controllable size and thickness. Here, we demonstrate the growth of single-crystalline GeSe nanoribbons by a vapor-liquid-solid process over Au catalyst on different substrates at low thermal budget. The nanoribbons crystallize in a layered structure, with ribbon axis along the armchair direction of the van der Waals layers. The ribbon morphology is determined by catalyst driven fast longitudinal growth accompanied by lateral expansion via edge-specific incorporation into the basal planes. This combined growth mechanism enables temperature controlled realization of ribbons with typical widths of up to 30 μm and lengths exceeding 100 μm, while maintaining sub-50 nm thickness. Nanoscale cathodoluminescence spectroscopy on individual GeSe nanoribbons demonstrates intense temperature-dependent band-edge emission up to room temperature, with fundamental bandgap and temperature coefficient of Eg(0) = 1.29 eV and α = 3.0 × 10-4 eV K-1, respectively, confirming high quality GeSe with low concentration of non-radiative recombination centers promising for optoelectronic applications including light emitters, photodetectors, and solar cells.

Multiphoton intersubband transitions in an armchair graphene nanoribbon

We present an analytical approach to the problem of the interband transitions in an armchair graphene nanoribbon (AGNR), exposed to the time-periodic electric field of strong light wave, polarized parallel to the ribbon axis. The two-dimensional Dirac equation for the massless electron subject to the ribbon confinement is employed. In the resonant approximation the probability of the transitions between the valence and conduction size-quantized subbands are calculated in an explicit form. We trace the dependencies of the Rabi frequency for these transitions on the ribbon width and electric field strength for both the multiphoton-assisted and tunneling regimes relevant to the fast oscillating and practically constant electric field, respectively. Estimates of the expected experimental values for the typically employed AGNR and laser technique facilities show that the Rabi oscillations can be observed under laboratory conditions. The data, corresponding to the intersubband tunneling, makes the AGNR a 1D condensed matter analog, in which the quantum electrodynamic vacuum decay can be detected by the employment of the attainable electric fields.

Strain-induced switching in field effect transistor based on zigzag graphene nanoribbons

In this paper, we investigate the effects of uniaxial and oblique strain on Non-linear transport of zigzag graphene nanoribbons using non-equilibrium Green's function formalism. The current-voltage characteristics and especially negative differential resistance (NDR) are affected by the type, strength, and direction of the applied strain. For the tensile strain along the ribbon axis, the on-off current ratio increases, while for the compressive strain, NDR gradually disappears. In the oblique strain, the on-off current ratio drastically decreases compared to the un-strained case. In context, we demonstrate how strain can affect band structure and transition rules as well as transmission coefficients. Also in our calculations, we consider Coulomb interaction as long-range electrostatic potential at mean-field approximation. Coulomb interaction decreases off current and leads to the increased on-off current ratio in the oblique strain. Here, we observe under the influence of the oblique strain, the geometrical symmetry is broken, so the symmetry of charge profile and local currents are broken across ZGNR. We show an imbalanced accumulated charge located on the nanoribbon edges that as a consequence, appear some transverse local currents between the upper and lower edges. These transverse local currents are increased by the strain strength. The minimum (maximum) imbalanced charge accumulated on the ribbon edges occurs exactly at the on (off)-state of longitudinal bias where the transverse current is decreasing (increasing). Finally, we strongly suggest the strain can operate as a nanoelectromechanical switch.

Multiscale Magnetic Anisotropy in Amorphous Ferromagnetic Ribbon: An Example of FeCuNdSiB Alloy

An understanding of the magnetic properties in an amorphous alloy requires comprehensive studies of magnetic anisotropy at various scales. In this paper such a study is carried out using amorphous ribbons FeCuNbSiB. The magnetic anisotropy associated with the rolling axis of ribbons does not affect hysteresis loop measurements, but the disappearance of a fingerprint-like pattern in the domain structure occurs in different fields when they are applied along and transverse the rolling axis. A correlation between the local magnetic anisotropy constant and the nanoscale within which the local easy axis is ordered was found.

Graphene gets bent

Graphene gets bent

Two Dimensional Oblique Molecular Packing within a Model Peptide Ribbon Aggregate

A10K (A=alanine, K=lysine) model peptides self‐assemble into ribbon‐like β‐sheet aggregates. Here, we report an X‐ray diffraction investigation on a flow‐aligned dispersion of these self‐assembly structures. The two‐dimensional wide‐angle X‐ray scattering pattern suggests that peptide pack in a two‐dimensional oblique lattice, essentially identical to the crystalline packing of polyalanine, An (for n>4). One side of the oblique unit cell, corresponding to the anti‐parallel β‐sheet, is oriented along the ribbon's axis. Together with recently published small angle X‐ray scattering data of the same system, this work thus yields a detailed description of the self‐assembled ribbon aggregates, down to the molecular length scale. Notably, our results highlight the importance of the crystalline peptide packing within its self‐assembly aggregates, which is often neglected.

Surface Magnetostriction of FeCoB Amorphous Ribbons Analyzed Using Magneto-Optical Kerr Microscopy.

Surface sensitive magneto-optical Kerr microscopy completed with the special self-made sample holder is used for studying the magneto-elastic behaviour in the surface of the as-quenched amorphous Fe73Co12B15 alloy. The 10, 5, and 3 mm wide and approximately 34 μm thick ribbons were prepared by the conventional planar flow casting process. The experimental setup allows for a simultaneous application of an external magnetic field in the directions parallel and perpendicular to the ribbon axis and of compression stress from one side of the sample, resulting in tensile stress in opposite side. The distributions of tensile stresses in the measured surface were modelled by the finite element method. The observed changes of the magnetic domains and hysteresis loop anisotropy field under applied stress are evaluated using the Becker–Kersten method. This resulted in the determination of the local surface magnetostrictive coefficient from an area of about 200 μm in diameter. The obtained values ranged between 37–60 ppm and were well comparable with the bulk value presented in the literature.

Electronic structure and thermoelectric properties of Sn1.2−xNbxTi0.8S3 with a quasi-one-dimensional structure

We report the electronic structure and thermoelectric properties of a tin titanium trisulfide, Sn1.2Ti0.8S3. The crystal structure is composed of infinite “ribbons” of double edge-sharing (Sn4+/Ti4+)S6 octahedra capped by Sn2+. First-principles calculations predict a nearly unidirectional transport of electrons along the ribbon axis for a single crystal and the existence of lone-pair electrons on Sn2+. Experiments on polycrystalline pressed samples demonstrate that Sn1.2Ti0.8S3 exhibits semiconducting temperature dependence of electrical resistivity and a large negative Seebeck coefficient at room temperature. Substitution of Nb5+ for Sn4+ at the octahedral sites increases the electron carrier concentration, leading to an enhancement of the thermoelectric power factor. Anisotropy in the electronic properties is weak because of a weak orientation of the ribbon axis of crystallites in the pressed sample. The lattice thermal conductivity is less than 1 W K−1 m−1 for the pristine and substituted samples, which is attributed to weak bonding between the ribbons via the lone-pair electrons of Sn2+ and to random occupation of Sn4+, Ti4+, and Nb5+ at the octahedral sites.

Exciton absorption spectra in narrow armchair graphene nanoribbons in an electric field

We present an analytical investigation of the exciton optical absorption in a narrow armchair graphene nanoribbon (AGNR) in the presence of a longitudinal external electric field directed parallel to the ribbon axis. The two-body 2D Dirac equation for the massless electron and hole subject to the ribbon confinement, Coulomb interaction and electric field is employed. The ribbon confinement is assumed to be much stronger than the internal exciton electric field which in turn considerably exceeds the external electric field. This justifies an adiabatic approximation implying a slow longitudinal and fast transverse electron-hole relative motion governed by the exciton attraction and accompanied by the external electric field and ribbon confinement effects, respectively. In the single subband approximation of the isolated size-quantized subbands induced by the ribbon confinement the exciton electroabsorption coefficient is determined in an explicit form. The pronounced dependencies of the exciton peak positions, widths and intensities on the ribbon width and electric field strength are traced. The electron-hole exciton attraction modifies remarkably the Franz-Keldysh electroabsorption in the frequency region both below and above the edges determined by the size-quantized energy levels. In the double-subband approximation of the interacting ground and first excited subbands the combined effect of the exciton electro- and autoionization caused by the electric field and intersubband coupling, respectively, are explored. Estimates of the expected experimental values for the typically employed AGNR show that for a weak electric field the exciton quasi-discrete states remain sufficiently stable to be observed in optical experiments, while relatively strong fields free the captured carriers to further restore their contribution to the transport.

Magnetic Properties of the Fe63.5Ni10Cu1Nb3Si13.5B9 Alloy Nanocrystallized in the Presence of Tensile Stresses

The effect of 10 at % Ni, which was introduced into the classic Finemet Fe73.5Cu1Nb3Si13.5B9 at the expense of the Fe content, on the magnetic properties of the composition has been considered. The alloy was subjected to nanocrystallizing annealing in the presence of tensile stresses and in their absence. It is shown that, similarly to the Ni-free alloy, in the Fe63.5Ni10Cu1Nb3Si13.5B9 alloy subjected to thermomechanical treatment, the magnetic anisotropy with the easy magnetization direction across the ribbon axis (transverse induced magnetic anisotropy) is induced. It was found that the 10 at % Ni addition almost does not affect the value of magnetic anisotropy constant induced under thermomechanical treatment and decelerates the process of magnetic anisotropy inducing at σ ≤ 200 MPa. The Ni-containing alloy subjected to nanocrystallizing annealing (at 520°C) in the presence of tensile stresses and in their absence demonstrates the more than 200-fold increase in the coercive force as the annealing time increases from 1 to 4 h, whereas the coercive force of the Ni-free alloy is almost unchanged. This is likely to be related to the appearance of new structural components in the Ni-alloyed composition upon annealing.

Ab initio study of the structural, electronic, magnetic, and optical properties of silicene nanoribbons

We present first-principles calculations of structural, electronic, magnetic, and optical properties of zigzag-oriented silicene nanoribbons, which, being endowed with spin-polarized edge states, are promising candidates as building blocks of future spintronic devices. The minimal width for a structurally stable planar structure having zigzag edges corresponds to a 4-chain ribbon, whose ground state presents antiferromagnetically coupled spin-polarized edges, and a lattice parameter along the nanoribbon axis contracted ($\ensuremath{\sim}5%$) with respect to the bulk value. Starting from the dependence of structural and electronic properties on the ribbon width, we present theoretical predictions for the optical spectra of narrow nanoribbons, in which excitonic effects are relevant due to the confinement in a quasi-one-dimensional structure. Especially for light polarized parallel to the ribbon axis, we find significant differences in the position of optical absorption peaks of ribbons with ferro- or antiferromagnetically coupled edges, showing that optical spectra can be used as a fingerprint of the magnetic coupling of electronic edge states.

Effects of the angle between magnetic field and ribbon axis on the magneto-impedance properties of amorphous FeSiB/Cu/FeSiB sandwiched ribbon

Amorphous FeSiB ribbons with nominal composition of Fe<sub>78</sub>Si<sub>9</sub>B<sub>13</sub> are prepared by single roll rapid quenching technique. In order to enhance the giant magneto-impedance (GMI) effect of FeSiB ribbons, interlaminar gluing method is used to produce FeSiB/Cu/FeSiB sandwiched structure in which the FeSiB ribbons act as external soft magnetic layers and the Cu foil acts as internal conductive layer. The variation characteristics of GMI with angle <inline-formula><tex-math id="M7">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M7.png"/></alternatives></inline-formula> between the external magnetic field and the ribbon axis for the single layer FeSiB ribbon and the sandwiched ribbon are studied by a rotating device placed in magnetic field which can drive the sample to rotate, to obtain a variable angle <inline-formula><tex-math id="M8">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M8.png"/></alternatives></inline-formula> from 0° to 90° with 15° degree angle interval. Magnetic domain structure detection shows that the amorphous FeSiB ribbons have near-axial magnetic anisotropy, and the angle between easy axis and ribbon axis is about 15°. In this work, in the case without considering the effects of shape anisotropy, the functional relationship among magnetic field at anisotropic peak of permeability, transverse permeability ratio and angle <inline-formula><tex-math id="M9">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M9.png"/></alternatives></inline-formula> is obtained according to the expression of the transverse permeability of ribbon derived from a domain rotation model. The results display that anisotropic peak appears in the transverse permeability for each of all testing values of angle <inline-formula><tex-math id="M10">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M10.png"/></alternatives></inline-formula>. Moreover, the transverse permeability ratio increases with <inline-formula><tex-math id="M11">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M11.png"/></alternatives></inline-formula> increasing. The magneto-impedance testing results indicate that the maximum GMI ratio of single layer ribbon is only about 30% at an optimum response frequency of 7.0 MHz, and angle <inline-formula><tex-math id="M12">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M12.png"/></alternatives></inline-formula> has almost no influence on the GMI. In contrast, the GMI of sandwiched ribbon presents a significant enhancement, the maximum value of the longitudinal GMI ratio and that of transverse GMI ratio reach 272% and 464%, respectively at an optimum response frequency of 0.6 MHz, the GMI of sandwiched ribbon is sensitive to the variation of angle <inline-formula><tex-math id="M13">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M13.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M13.png"/></alternatives></inline-formula>, and with increase of <inline-formula><tex-math id="M14">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M14.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M14.png"/></alternatives></inline-formula> the GMI increases accordingly. In addition, for all testing values of angle <inline-formula><tex-math id="M15">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M15.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M15.png"/></alternatives></inline-formula>, the GMI profiles of sandwiched ribbon show anisotropic peaks, due to the influence of transverse demagnetization field, and the anisotropic peak broadens with the increase of angle <inline-formula><tex-math id="M16">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M16.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M16.png"/></alternatives></inline-formula>. By comparing the theoretical and experimental results, it can be concluded that for the sandwiched ribbon, the characteristics of GMI changing with angle <inline-formula><tex-math id="M17">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M17.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M17.png"/></alternatives></inline-formula> agree better with the theoretical transverse permeability, which but is not for single layer ribbon. Besides, whether the anisotropic peak of GMI appears is independent of the orientation of the external magnetic field. As the transverse permeability ratio increases with the increase of angle <inline-formula><tex-math id="M18">\begin{document}$\beta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M18.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20181806_M18.png"/></alternatives></inline-formula>, the GMI effect of sandwiched ribbon is enhanced accordingly. The study results also demonstrate that the domain rotation model can be used to explicate the variation of GMI properties of sandwiched ribbon with the angle between magnetic field and ribbon axis qualitatively when the domain rotation magnetization is dominant.

Optical properties of shortest-width zig-zag silicene nano-ribbons: Effects of local fields

Abstract We have computed from first principles the structural, magnetic and optical properties of zig-zag oriented silicene nanoribbons. The minimal width for structurally stable planar structure having zig-zag edges corresponds to a 4-chains ribbon. Its ground state presents reconstructed and spin polarized edges, coupled antiferromagnetically. For this state, and for the corresponding excited state with ferromagnetically coupled edges, we computed the optical absorption spectra within the independent particle approximation, including local field effect corrections, for light polarized in the directions parallel and perpendicular to the ribbon axis. For the “parallel” light polarization the inclusion of local fields effects is limited to a slight reduction of the intensity of the main peak in the infrared region, as well as that of some minor peaks in the visible-ultraviolet structure. Conversely, the computed optical spectrum for light polarized perpendicularly to the ribbon axis shows that the short-width zig-zag nanoribbons are basically transparent in the infrared and visible region, because of the effect of electronic confinement combined with local fields.