Ribbon Plane Research Articles

Mössbauer analysis of (FeNiCrSiB) amorphous alloy ribbons

The fabrication of iron-based amorphous alloys was executed through the utilization of the melt-spinning technique, followed by a characterization employing X-ray diffraction (XRD), scanning electron microscopes (SEM) and transmission Mössbauer spectroscopy (MS). The studies were performed on Fe76-xNixCr4Si8B12 (where x = 0, 4, 12, and 30) metallic glasses in the form of ribbons. Mössbauer spectroscopy enables the exploration of the localized surroundings of iron (Fe) atoms within the glassy state, revealing alterations in the amorphous structure attributed to variations in the addition of Nickel (Ni). The broad lines in the Mössbauer spectra of ferromagnetic amorphous ribbons are a result of the distribution of non-equivalent iron sites and interatomic distances. The line intensity ratio suggests a preferential orientation of iron moments within the ribbon plane. The results derived from Mössbauer analysis indicate that the amorphous alloys feature bimodal distributions of the hyperfine fields. Changes in the nickel content within the alloys impact the disorder in the as-cast state and concurrently influence parameters such as the average hyperfine field <Hhyp>, the average radius R of the first coordination shell, and the number of nearest neighbor Fe atoms.

Effect of moderate Fe doping and heat treatment on the microstructure of Ni-Mn-Ga melt-spun ribbons

The present work investigates the effects of Mn substitution with additions of Fe (0.5, 1, 2, and 3 at%) on the crystal structure, phase transformation temperatures, and magnetic properties of casted and heat-treated Ni49.8Mn28.5−xGa21.7Fex magnetic shape memory (MSM) alloys. The alloys doped with 0.5 and 1 at% Fe exhibited single-phase seven-layered modulated (14 M) and five-layered modulated (10 M) martensite structures at ambient temperature, whereas the alloys doped with 2 and 3 at% Fe exhibited L21 Heusler austenite structures at ambient temperature. The Ni49.8Mn27.5Ga21.7Fe1 alloy exhibiting the 10 M crystal structure at ambient temperature was selected for making ribbons using the melt-spinning process. The effects of heat treatment on grain growth, crystal structure, and other functional properties of the melt-spun ribbons were studied. The ribbons heat-treated at 1273 K exhibited a 10 M martensite structure and an average grain size of 220 µm along the ribbon plane. The results show that Ni49.8Mn27.5Ga21.7Fe1 is a particularly promising composition for designing and manufacturing functional MSM micro-actuators.

Excluded checkerboard colourable ribbon graph minors

Motivated by the Eulerian ribbon graph minors, in this paper we introduce the notion of checkerboard colourable minors for ribbon graphs and its dual: bipartite minors for ribbon graphs. Motivated by the bipartite minors of abstract graphs, another bipartite minors for ribbon graphs, i.e. the bipartite ribbon graph join minors are also introduced. Using these minors then we give excluded minor characterizations of the classes of checkerboard colourable ribbon graphs, bipartite ribbon graphs, plane checkerboard colourable ribbon graphs and plane bipartite ribbon graphs.

Strongly localized states and giant optical absorption induced by multiple flat-bands in AA-stacked multilayer armchair graphene nanoribbons

We propose an AA-stacked multilayer graphene nanoribbon with two symmetrical armchair edges as a multiple flat-band (FB) material. Using the tight-binding Hamiltonian and Green’s function method, we find that the FBs are complete and merged into many dispersive bands. The FBs cause multiple strongly localized states (SLSs) at the sites of the odd lines in every sublayer and a giant optical absorption (GOA) at energy point 2t, where t is the electronic intralayer hopping energy between two nearest-neighbor sites. By driving an electric field perpendicular to the ribbon plane, the bandgaps of the FBs are tunable. Accordingly, the positions of the SLSs in the energy regime can be shifted. However, the position of the GOA is robust against such field, but its strength exhibits a collapse behavior with a fixed quantization step. On the contrary, by driving an electric field parallel to the ribbon plane, the completeness of FBs is destroyed. Resultantly, the SLSs and GOA are suppressed and even quenched. Therefore, such ribbons may be excellent candidates for the design of the controllable information-transmission and optical-electric nanodevices.

Effects of vertical electric field and charged impurities on the spin-polarized transport ofβ-antimonene armchair nanoribbons

The electronic properties of antimonene, single-layer Sb, are attracting great attention. In this paper, spin transport in armchair antimonene nanoribbon (ASbNR) is investigated. Following the tight-binding model, we calculate both the transmission probability and the conductance by means of the non-equilibrium Green's function (NEGF) method. The effects of an external electric field vertical to the ribbon plane are explored. Our results indicate that the spin-flip rate increases with the vertical electric field. Disorder effects on spin transport are addressed by considering the presence of charged impurities. It is found that charged impurities also enhance the spin-flip rate but to a lesser extent than the out-of-plane electric field.

Magnetic Properties of Rapidly Quenched Soft Magnetic Co-Based Alloy Subjected to Heat Treatment in a Sulfur Atmosphere

The effect of heat treatments (HTs) in a sulfur atmosphere of a rapidly quenched soft magnetic 71KNSR (Co72Ni12.2Fe5.7Si6.5B3.6) alloy on its magnetic properties is studied in this work. The alloy under study is subjected to HTs at temperatures above and below its Curie temperature. It is shown that the magnetic properties are improved in both cases. It is likely that the improvement is traceable to the relaxation of internal quenching stresses in the course of heat treatment. X-ray diffraction studies performed after HT in a sulfur atmosphere at 350°С showed up the appearance of cobalt sulfide, which can inducing additional tensile stresses. This results in a decrease in the volume of domains with the magnetization perpendicular to the ribbon plane, which, in turn, explains the more substantial improvement of the magnetic properties of the Co72Ni12.2Fe5.7Si6.5B3.6 ribbon after HT in the sulfur atmosphere at the temperature above the Curie temperature.

Cathodoluminescence of Ultrathin Twisted Ge1- x Snx S van der Waals Nanoribbon Waveguides.

Ultrathin van der Waals semiconductors have shown extraordinary optoelectronic and photonic properties. Propagating photonic modes make layered crystal waveguides attractive for photonic circuitry and for studying hybrid light-matter states. Accessing guided modes by conventional optics is challenging due to the limited spatial resolution and poor out-of-plane far-field coupling. Scanning near-field optical microscopy can overcome these issues and can characterize waveguide modes down to a resolution of tens of nanometers, albeit for planar samples or nanostructures with moderate height variations. Electron microscopy provides atomic-scale localization also for more complex geometries, and recent advances have extended the accessible excitations from interband transitions to phonons. Here, bottom-up synthesized layered semiconductor (Ge1- x Snx S) nanoribbons with an axial twist and deep subwavelength thickness are demonstrated as a platform for realizing waveguide modes, and cathodoluminescence spectroscopy is introduced as a tool to characterize them. Combined experiments and simulations show the excitation of guided modes by the electron beam and their efficient detection via photons emitted in the ribbon plane, which enables the measurement of key properties such as the evanescent field into the vacuum cladding with nanometer resolution. The results identify van der Waals waveguides operating in the infrared and highlight an electron-microscopy-based approach for probing complex-shaped nanophotonic structures.

Phase transformation and magnetocaloric effect of Co-doped Mn–Ni–In melt-spun ribbons

Ribbon-shaped magnetocaloric materials are favorable to achieve high heat-transfer efficiencies due to their large specific surface area. In this work, Mn50Ni41−xIn9Cox (0 ≤ x ≤ 4) ribbons were prepared using a melt-spinning technique, and the corresponding phase transformation and magnetocaloric properties were studied. The large temperature gradient during melt-spinning caused the initial austenite in the ribbons to form typical columnar-shaped grains with a strong ⟨001⟩A preferred orientation perpendicular to the ribbon plane. After cooling, the ribbons undergo martensitic transformation from cubic austenite to monoclinic eight-layered modulated (8 M) martensite. High angle annular dark field-scanning transmission electron microscopy observations indicate that martensite lattice modulation is inhomogeneous at atomic scales. Co substitution for Ni not only strongly influences the phase transformation temperatures but also greatly enhances ferromagnetic coupling. As a result, an enlarged magnetization difference across the martensitic transformation under a field change of 5 T in the Mn50Ni38In9Co3 ribbon induces a large magnetic entropy change up to 12.1 J kg−1 K–1 and a refrigeration capacity of 197 J kg–1 around room temperature. In addition, a wide operational temperature region up to 31 K is obtained in the Mn50Ni37In9Co4 ribbon due to the enhanced sensitivity of the transformation temperature shift under a magnetic field.

Effect of Chemically Active Medium on Magnetic Characteristics of Soft Magnetic Co-Based Amorphous Alloy

The interaction of the ribbon surface with acetone and its effect on the magnetic characteristics of ribbon are studied in this work using the example of soft magnetic Co-based AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) amorphous alloy. The studies show the different effect of acetone treatment of ribbon on the magnetization distribution and magnetic permeability of material in states differing in the sign of saturation magnetostriction. The treatment of the ribbon in the state with λs > 0 favors the increase in both the volume of domains with the orthogonal magnetization and the magnetic texture sharpness in the ribbon plane; in the state with λs < 0, the treatment favors the decrease in both the volume of domains with the orthogonal magnetization and magnetic texture sharpness and an increase in the maximum magnetic permeability. This can result from the predominantly planar anisotropic compressive stresses induced in the ribbon by catalytic oxidation and hydrogenation of acetone.

Low-Noise Fundamental-Mode Orthogonal Fluxgate Magnetometer Built With an Amorphous Ribbon Core

Room temperature operating magnetometers able to detect a few pT magnetic field would play a crucial role in such areas as bio-magnetic field detection and very tiny ferromagnetic contaminats detection in battery production lines. We have already reported fundamental mode orthogonal fluxgate having a noise density $\sim 3$ pT$/ \surd $ Hz at 1 Hz using a Co-based amorphous wire (made by Unitika) core sensor head [1]. However, the supply of the amorphous wire is limited. In this paper, we present that the narrow amorphous ribbon core is an alternative to the wire core if the dc bias current for the fundamental mode operation [2] is properly adjusted. In a particular case of as-cast Metglas 2714A ribbon of 1 mm width, the dc bias current elevated to 200 mA, which is to be 40 mA for the wire core sensor head, reduces the noise down to a few pT$/ \surd $ Hz. In the experiment, we made several sensor heads listed in Table I using the above mentioned ribbon. A 1 mm width ribbon which is made by slitting a wider sample is bent in a U-shape or more likely in a hair-pin shape and inserted into a cylindrical pickup coil of length 30 mm, bore diameter of 2 mm and having 500 turn copper winding. The driving and signal processing electronics used is the one developed for the wire core sensor head. The only difference is that an adopter circuit is inserted between the ribbon core sensor head and the driving electronics to supply a large dc bias current from the battery and to moderately $( \approx 2\mathrm {x})$ amplify the ac excitation current; the ac excitation current for ribbon core sensor heads is 24 mArms while that for wire core one is 12 mArms. The driving frequency is 100 kHz and the magnetometer is configured to operate in a closed loop (feedback) using $\mathrm {a}10 \mathrm {k}\Omega $ feedback resistor. The sensitivity increases slightly with increase in length of the core, because the demagnetization effect becomes smaller for longer cores. The sensitivity of the magnetometer with the wire core sensor head is about one half of that of the magnetometer with the ribbon core sensor head because the number of turns of the pickup coil used for the wire core is 1000. It should be noted that the sensitivity of the closed loop system is $R/ n[\mathrm {V} /\text{A}$/m] where $R$ is the feedback resistance and $n$ is the winding density per meter of the pickup coil. The noise spectral density of the magnetometer was measured by placing the sensor head in a five shell cylindrical shield and by using an FFT analyzer (Stanford Research Systems SR780). Results are listed in Table I from which we can conclude that the noise level obtained with a ribbon core sensor head is comparable to that obtained with a wire core sensor head. Fig. 1 shows the noise spectral density of the ribbon core sensor head R19 for three different dc bias currents. It is interesting to see that the noise level is dramatically reduced by increasing the dc bias current. This is probably related to the nature of the as-cast Metglas 2714A ribbon such that weak magnetic anisotropies are distributed randomly in the ribbon plane. It is also interesting to compare the magnetic field produced by the dc bias current at surfaces of the ribbon core and of the wire core. For the wire core, the radius is about $60 \mu \mathrm {m}$ and the bias current is 40 mA, hence the magnetic field is about 106 A/m. For the ribbon core, because the thickness $( < 20 \mu \mathrm {m})$ is negligible compared to the width (1 mm), the magnetic field at the surface of the ribbon is quite uniform along the width direction, hence the magnetic field can be calculated by dividing the current (220 mA) by the peripheral length which is twice the width, yielding 110 A/m which is similar to the one for the wire. One may expect that necessary dc bias current can be reduced by making the width of the ribbon narrower. A very weak magnetic field of rectangular waveform of 15 pT in peak-to-peak is well detected with a short averaging. Details on the adapter circuit will be explained.

Magnetization Processes in Ribbons of Soft Magnetic Amorphous Alloys

Using iron-based (Fe–B–Si–C; Fe–Ni–Si–B) and cobalt-based (Co–Fe–Ni–Cr–Mn–Si–B) soft magnetic alloys as examples, we have studied the dependences of the remanence measured using minor hysteresis loops on the maximum induction. The different degrees of stabilization of the 180° and 90° domain walls allows these dependences to be used to analyze the magnetization processes that occur in the rapidly quenched soft magnetic alloys. It has been established from the Br(Bm) dependences that, in the ribbons of soft magnetic amorphous alloys, the processes of the rotation of the magnetization oriented perpendicular to the ribbon plane start before the end of the processes of the displacement of the walls of domains with planar magnetization. After the end of the magnetization rotation processes, the magnetization processes can be interpreted as the displacement of the domain walls with a planar magnetization accompanied by a decrease in their number and a transition to a bistable state.

Adsorbing the magnetic superhalogen MnCl3 to realize intriguing half-metallic and spin-gapless-semiconducting behavior in zigzag or armchair SiC nanoribbon.

By means of first-principles computations, we first propose a new and effective strategy through adsorbing the magnetic superhalogen MnCl3 to modulate the electronic and magnetic properties of zigzag- and armchair-edged SiC nanoribbons (zSiCNR and aSiCNR, respectively). In view of its large intrinsic magnetic moment and strong electron-withdrawing ability, the adsorption of magnetic superhalogen MnCl3 can introduce magnetism in the substrate SiCNR, and simultaneously induce the electron transfer process from SiCNR to MnCl3, resulting in the evident increase of electrostatic potential in the ribbon plane, like applying an electric field. As a result, the magnetic degeneracy of pristine zSiCNR can be broken and a robust ferromagnetic half-metallicity or metallicity can be observed in the modified zSiCNR systems, while a robust ferromagnetic half-metallic or spin-gapless-semiconducting behavior can be obtained in the modified aSiCNR systems. Note that both the appealing half-metallicity and spin-gapless-semiconductor behavior are key features which hold promise for future spintronic applications. Moreover, all of these new superhalogen–SiC nanosystems can possess considerably high structural stabilities. These intriguing findings will be advantageous for promoting excellent SiC-based nanomaterials in the applications of spintronics and multifunctional nanodevices in the near future.

Effect of cobalt doping on martensitic transformations and the magnetic properties of Ni50−xCoxMn37Sn13 (x = 1, 2, 3) Heusler ribbons

The effect of cobalt doping on martensitic transformations and the magnetic properties of Ni50−xCox Mn37Sn13 (x = 1, 2, 3) magnetic shape memory alloys obtained by melt spinning in the form of ribbons is studied. The crystallographic structure of all of the ribbons at room temperature is austenite cubic L21. SEM micrographs indicate the formation of textured ribbons with columnar grains growing up perpendicular to the ribbon plane. For all of the ribbons, DSC cyclic scans reveal the martensitic transformation on cooling and the reverse austenitic transformation upon heating below room temperature. In addition, they indicate that the martensitic transformation temperatures decrease with an increasing cobalt content.Thermomagnetic curves reveal the coexistence of AFM and FM exchange interactions at low temperatures. Likewise, the magnetization change (ΔM) between the martensite and austenite phase, as well as the austenite Curie temperature (TCA), increase with increasing cobalt content in the ribbons. Structural transformations are also sensitive to the external applied magnetic field. This fact suggests that the structural transformation temperatures of the ribbons could be tuned to the desired functional temperature by controlling the cobalt amount through the replacement of Ni as well as by changing the applied magnetic field, which could lead to an enhancement of the magnetic properties.

Characterization of the kinetic arrest of martensitic transformation in Ni45Co5Mn36.8In13.2 melt-spun ribbons

The kinetic arrest (KA) of martensitic transformation (MT) observed in Ni45Co5Mn36.8In13.2 melt-spun ribbons has been studied. These alloy ribbons show an ordered columnar-like grain microstructure with the longer grain axis growing perpendicular to ribbon plane and transform martensitically from a single austenitic (AST) parent phase with the L21-type crystal structure to a monoclinic incommensurate 6M modulated martensite (MST). Results show that the volume fraction of austenite frozen into the martensitic matrix is proportional to the applied magnetic field. A fully arrest of the structural transition is found for a magnetic field of 7T. The metastable character of the non-equilibrium field-cooled glassy state was characterized by introducing thermal and magnetic field fluctuations or measuring the relaxation of magnetization. The relaxation of magnetization from a field-cooled kinetically arrested state at 5 and 7T follows the Kohlrausch–Williams–Watts (KWW) stretched exponential function with a β exponent around 0.95 indicating the weak metastable nature of the system under the strong magnetic fields. The relationship between the occurrence of exchange bias and the frozen fraction of AST into the MST matrix was studied.

Robust and controllable electronic local transports in armchair silicene nanoribbons under a perpendicular electric field

We study the electronic local distribution and transports in pristine armchair-edge silicene nanoribbons (ASiNRs) based on the tight-binding approximation. By calculating the local densities of states at different sites and the bond current between two adjacent sites, we show that comparing to the pristine armchair-edge graphene nanoribbons, a similar “[Formula: see text]” rule and multiple low-electron transport channels exist in the pristine [Formula: see text]-ASiNRs. However, differently, they are controllable to appear and disappear by applying an electric field perpendicular to the ribbon plane. Therefore, one can manipulate the semiconducting channels and realize the current switch “on/off,” unchanging their structures. Moreover, the results are robust against the edge-passivation and a few structural defects, which ensures their stability for the practical application in the silicene-based device.

Mössbauer spectroscopy research on magnetic softening of Fe84B10C6 amorphous alloy during low-temperature annealing

The mechanism of magnetic softening in Fe84B10C6 amorphous alloys annealed at a temperature below the crystallization temperature has been investigated by Mössbauer spectroscopy. With the prolongation of annealing time, saturation flux density increases gradually but coercivity firstly declines to a minimum and then increases drastically. All the modulations of local structure strengthen the magnetic exchange between Fe neighbor atoms during low-temperature annealing. The structural relaxation at the early stage of annealing including annihilation of excess free volume and residual stress rotates the easy axis to the ribbon plane and weakens magnetic anisotropy, while the subsequent structural relaxation contributing to chemical inhomogeneity results in the inverse situation. Thus, appropriate annealing can magnetically soften amorphous alloys. For the Fe84B10C6 amorphous alloy, soft magnetic properties are optimized when annealed at 493 K for 100 s.

Anisotropic nanocrystalline SmCo4.8Cr0.12C0.08 permanent magnets fabricated using melt-spinning method

Anisotropic CaCu5-type SmCo4.8Cr0.12C0.08 alloys with a dendritic nanostructure and an out-of-plane <0001> texture were fabricated using the melt-spinning method at a speed of 50 m/s. The microstructure changed from randomly orientated equiaxial grains for the ribbon melt-spun at 30 m/s to dendritic ones for that spun at 50 m/s. High-angle annular dark-field scanning transmission electron microscopy and X-ray energy dispersive spectroscopy analysis reveal that the distribution of carbon in SmCo5 grains obtained at higher speeds is highly inhomogeneous and leads to the formation of C-depleted and C-rich dendrite structure with a [0001]C−richSmCo5∥[0001]C−depletedSmCo5 orientation relationship. Moreover, the incorporation of C into the SmCo5 phase helps to increase the Curie temperature to about 845 °C. A high coercivity of 40.3 kOe and a relatively high remanence of 42.0 emu/g were measured in the direction normal to the ribbon plane.

Spin polarization in Cu2MnSn Heusler alloy produced by melt-spinning

We report on magnetism, transport and spin polarization characteristics of the melt-spun Cu2MnSn alloy prepared by the rapid quenching technique. The as- cast ribbons showed a relatively well ordered chemical composition (Cu = 50.4%, Mn = 27.1%, Sn = 22.5%). The structural characterization by using X-ray diffraction shows L21/B2 crystalline structure with the lattice parameter a = 6.196 Å. The magnetic and transport measurements show a metallic behavior with the Curie temperature of 530 K and reveal anisotropic character with the easy magnetization plane parallel with respect to the ribbon plane. As-cast Cu2MnSn ribbons show the spin polarization measured by using Andreev reflection technique within the range 68–75%.

On the magnetic anisotropy in Fe78Si9B13 ingots and amorphous ribbons: Orientation aligning of Fe-based phases/clusters

Magnetic anisotropy in Fe-based amorphous ribbon plays an important role in various applications and is still not fully understood. To gain an in-depth understanding of this phenomenon, the structure and magnetic properties of Fe78Si9B13 master alloy ingots and melt-spun amorphous ribbons were measured by various techniques. For the ingot samples, both the &amp;lt;100&amp;gt;α-Fe and &amp;lt;001&amp;gt;Fe2B axes are aligned parallel with the radial direction (RD) of the original cylindrical ingot, i.e. the maximum temperature gradient direction, and their other orthogonal axes have several preferred directions in the plane vertical to RD. The hard magnetic axis of the ingot samples is parallel to RD, which is due to the large magnetocrystalline anisotropy energy difference between &amp;lt;001&amp;gt; and {001} of the Fe2B phase. For the amorphous ribbons, there is an in-plane magnetic anisotropy: the easy or hard axis of magnetization is aligned on the plane of the ribbon, and parallel to or at an angle of about 60° to its width direction, respectively. According to the structural heredity between the melts and glasses/crystals during solidification, we deduce that the magnetic anisotropy in the ribbon plane is ascribed to the orientation alignment of Fe-Si and Fe-B clusters, i.e. a hidden order beyond short-range order, in Fe78Si9B13 amorphous ribbons.

Microstructure of as-cast single and twin roller melt-spun Ni2MnGa ribbons

Stoichiometric Ni2MnGa alloys are processed by two rapid solidification techniques – single-roller (SR) and twin-roller (TR) melt spinning – and the resulting microstructures and magnetic properties determined. Samples processed at tangential wheel speeds of 10m/s (V10) and 15m/s (V15) are studied in the as-cast condition to analyze the influence of the production methods on the microstructure. Important aspects like the resulting phases, their crystallographic texture, magnetic properties, martensitic transformation temperatures and Curie temperatures are compared. In addition, the magnetization mechanism involving twin boundary motion is explored. Our results indicate that the TR method provides lower cooling rates, thicker samples, higher internal stresses and larger MnS precipitates. However, the quenching rate is mainly determined by the tangential wheel velocity. TR samples also exhibit [100] texture normal to the ribbon plane but in a lesser extent than SR ribbons. Martensitic transformation temperatures are higher in samples V15 (~150K) than in V10 (~100K), with no clear difference between the SR and TR modes. This behavior is explained by considering distinct degrees of disorder in the L21 austenite phase resulting from quenching. The hysteresis of the transformation, defined as the difference Af−MS, takes similar values in the four samples analyzed. Pre-martensitic transformation temperatures are also slightly higher in samples V15, (230±3) K, than in samples V10, (222±3) K, as the magnitude of the Hopkinson effect, in good agreement with a higher residual stress level in TR ribbons. In the martensitic state, all ribbons exhibit hysteresis loops characteristic of a magnetization mechanism involving twin boundary motion. The switching magnetic fields for the onset of Type I twin boundary motion result between 220mT and 365mT, values equivalent to twinning stresses of about 1MPa. It is concluded that both procedures, SR and TR melt spinning, provide microstructures favoring magnetic field induced twin variant reorientation.