Theoretical Prediction and Experimental Validation of the Glass-Forming Ability and Magnetic Properties of Fe-Si-B Metallic Glasses from Atomic Structures

Developing new soft magnetic amorphous alloys with a low cost and high saturation magnetization (B_s) in a simple alloy system has attracted substantial attention for industrialization and commercialization. Herein, the glass-forming ability (GFA), thermodynamic properties, soft magnetic properties, and atomic structures of Fe_80+xSi_5−xB₁₅ (x = 0–4) amorphous soft magnetic alloys were investigated by ab initio molecular dynamics (AIMD) simulations and experiments. The pair distribution function (PDF), Voronoi polyhedron (VP), coordination number (CN), and chemical short- range order (CSRO) were analyzed based on the AIMD simulations for elucidating the correlations between the atomic structures with the glass-forming ability and magnetic properties. For the studied compositions, the Fe₈₂Si₃B₁₅ amorphous alloy was found to exhibit the strongest solute–solute avoidance effect, the longest Fe-Fe bond, a relatively high partial CN for the Fe-Fe pair, and the most pronounced tendency to form more stable clusters. The simulation results indicated that Fe₈₂Si₃B₁₅ was the optimum composition balancing the saturation magnetization and the GFA. This prediction was confirmed by experimental observations. The presented work provides a reference for synthesizing new Fe-Si-B magnetic amorphous alloys.     

Effect of Cu Substitution and Heat Treatment on Phase Formation and Magnetic Properties of Sm12Co88−xCux Melt-Spun Ribbons

The phase structure and microstructure of Sm₁₂Co_88−xCu_x (x = 0, 2, 4, 6, 8, 10; at.%) as-cast alloys and melt-spun ribbons prepared via the arc-melting method and melt-spun technology were studied experimentally by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results reveal that the Sm₁₂Co_88−xCu_x (x = 0) as-cast alloy contains Sm₂Co₁₇ and Sm₅Co₁₉ phases, while the Sm₁₂Co_88−xCu_x (x = 2) as-cast alloy is composed of Sm₂Co₁₇, Sm₂Co₇ and Sm(Co, Cu)₅ phases. Sm₂Co₁₇ and Sm(Co, Cu)₅ phases are detected in Sm₁₂Co_88−xCu_x (x = 4, 6, 8, 10) as-cast alloys. Meanwhile, Sm₁₂Co_88−xCu_x ribbons show a single SmCo₇ phase, which is still formed in the ribbons annealed at 1023 K for one hour. After annealed at 1123 K for two hours, cooled slowly down to 673 K at 0.5 K/min and then kept for four hours, the ribbons are composed of Sm₂Co₁₇ and Sm(Co, Cu)₅ phases. The magnetic measurements of Sm₁₂Co_88−xCu_x ribbons were performed by vibrating sample magnetometer (VSM). The results exhibit that the maximum magnetic energy product ((BH)_max), the coercivity (H_cj) and the remanence (B_r) of the Sm₁₂Co_88−xCu_x ribbons increase generally with the increase in Cu substitution. In particular, the magnetic properties of the ribbons annealed at 1123 K and 673 K increase significantly with the increase in Cu substitution, resulting from the increase in the volume fraction of the formed Sm(Co, Cu)₅ phase after heat treatment.     

Microstructure and Magnetic Properties of Nanocrystalline Fe60−xCo25Ni15Six Alloy Elaborated by High-Energy Mechanical Milling

In the present work, the effect of Si addition on the magnetic properties of Fe_60−xCo₂₅Ni₁₅Si_x (x = 0, 5, 10, 20, and 30 at%) alloys prepared by mechanical alloying was analyzed by X-ray diffraction and magnetic vibrating sample magnetometry and SQUID. The crystallographic parameters of the bcc-solid solutions were calculated by Rietveld refinement of the X-ray diffraction patterns with Maud software. Scanning electron microscopy (SEM) was used to determine the morphology of the powdered alloys as a function of milling time. It was found that the Si addition has an important role in the increase of structural hardening and brittleness of the particles (favoring the more pronounced refinement of crystallites). The resulting nanostructure is highlighted in accordance with the concept of the structure of defects. Magnetic properties were related to the metalloid addition, formed phases, and chemical compositions. All processed samples showed a soft ferromagnetic behavior (Hc ≤ 100 Oe). The inhomogeneous evolution of the magnetization saturation as a function of milling time is explained by the magnetostriction effective anisotropy and stress induced during mechanical alloying.     

Effect of Co Substitution and Thermo-Magnetic Treatment on the Structure and Induced Magnetic Anisotropy of Fe84.5−xCoxNb5B8.5P2 Nanocrystalline Alloys

In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe_84.5-xCo_xNb₅B_8.5P₂ (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on a semi-industrial scale by the melt-spinning technique. The subsequent nanocrystallization processes were carried out under different conditions (with/without magnetic field). The comprehensive studies have been carried out using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hysteresis loop analyses, vibrating sample magnetometry and Mössbauer spectroscopy. Moreover, the frequency (up to 300 kHz) dependence of power losses and permeability at a magnetic induction up to 0.9 T was investigated. On the basis of some of the results obtained, we calculated the values of the activation energies and the induced magnetic anisotropies. The X-ray diffraction results confirm the surface crystallization effect previously observed for phosphorous-containing alloys. The in situ microscopic observations of crystallization describe this process in detail in accordance with the calorimetry results. Furthermore, the effect of Co content on the phase composition and the influence of annealing in an external magnetic field on magnetic properties, including the orientation of the magnetic spins, have been studied using various magnetic techniques. Finally, nanocrystalline Fe_64.5Co₂₀Nb₅B_8.5P₂ cores were prepared after transverse thermo-magnetic heat treatment and installed in industrially available portable heating equipment.     

Effect of Pre-Oxidation Treatment on Corrosion Resistance of FeCoSiBPC Amorphous Alloy

In this paper, the corrosion resistance of FeCoSiBPC amorphous alloy after pre-oxidation and non-oxidation heat treatment is investigated. The corrosion behaviors of Fe₈₀Co₃Si₃B₁₀P₁C₃ amorphous alloys in 1 mol/L NaCl solution were investigated by the electrochemical workstation. The pre-oxidation heat treatment can improve the corrosion resistance of FeCoSiBPC amorphous alloy through an increase in the Ecorr value from −0.736 to −0.668 V, which makes it easy to reach a passive state. The corroded morphology and products of amorphous alloys were tested by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM/TEM analysis showed that, after pre-oxidation treatment, the oxide layer was divided into two layers: the inner layer was amorphous, the outer layer appeared crystalline, and the main oxide was Fe₂O₃. During the oxidation process, Co and P elements diffused from the inner layer to the outer layer, forming phosphorus and cobalt oxides with high corrosion resistance on the surface of the ribbon, thereby improving the corrosion resistance of the ribbon.     

Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg2Ni-type Alloy by Melt Spinning

Mg₂Ni-type Mg₂Ni_1−xCo_x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg₂Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio (R5a) of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio (R20d) from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10⁻¹¹ to 3.88 × 10⁻¹¹ cm²/s and the limiting current density I_L from 150.9 to 887.4 mA/g.     

Influence of Dissolving Fe–Nb–B–Dy Alloys in Zirconium on Phase Structure,Microstructure and Magnetic Properties

This paper refers to the structural and magnetic properties of [(Fe₈₀Nb₆B₁₄)_0.88Dy_0.12]_1−xZr_x (x = 0; 0.01; 0.02; 0.05; 0.1; 0.2; 0.3; 0.5) alloys obtained by the vacuum mold suction casting method. The analysis of the phase contribution indicated a change in the compositions of the alloys. For x < 0.05, occurrence of the dominant Dy₂Fe₁₄B phase was observed, while a further increase in the Zr content led to the increasing contribution of the Fe–Zr compounds and, simultaneously, separation of crystalline Dy. The dilution of (Fe₈₀Nb₆B₁₄)_0.88Dy_0.12 in Zr strongly influenced the magnetization processes of the examined alloys. Generally, with the increasing x parameter, we observed a decrease in coercivity; however, the unexpected increase in magnetic saturation and remanence for x = 0.2 and x = 0.3 was shown and discussed.     

Magnetic and Magneto-Caloric Properties of the Amorphous Fe92−xZr8Bx Ribbons

Magnetic and magnetocaloric properties of the amorphous Fe_92−xZr₈B_x ribbons were studied in this work. Fully amorphous Fe₈₉Zr₈B₃, Fe₈₈Zr₈B₄, and Fe₈₇Zr₈B₅ ribbons were fabricated. The Curie temperature (T_c), saturation magnetization (M_s), and the maximum entropy change with the variation of a magnetic field (−ΔS_m^peak) of the glassy ribbons were significantly improved by the boron addition. The mechanism for the enhanced T_c and −ΔS_m^peak by boron addition was studied.     

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe_1−xCo_x (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe₂O₄ and Fe₃O₄ phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe_0.25Co_0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (M_S) of the Fe_0.25Co_0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the M_S of the Fe_0.75Co_0.25 and Fe_0.50Co_0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing.     

Magnetic Anisotropy and Microstructure in Electrodeposited Quaternary Sn-Fe-Ni-Co Alloys with Amorphous Character

Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni and 13–17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, ⁵⁷Fe and ¹¹⁹Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3–20%) are correlated to the electrodeposition parameters (J_dep from −16 to −23 mA/cm² for DC, J_pulse from −40 to −75 mA/cm² for PP), the composition and the saturation magnetization (~52–73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both in DC and pulse plated alloy coatings.     

Study on the Magnetocaloric Effect of Room Temperature Magnetic Refrigerant Material La0.5Pr0.5(Fe1−xCox)11.4Si1.6 and the Effect Arising from Co Doping on Its Curie Temperature

The arc-melting method was adopted to prepare the compound La_0.5Pr_0.5(Fe_1−xCo_x)_11.4Si_1.6 (x = 0, 0.02, 0.04, 0.06, 0.08), and the magnetocaloric effect of the compound was investigated. As indicated by the powder X-ray diffraction (XRD) results, after receiving 7-day high temperature annealing at 1373 K, all the compounds formed a single-phase cubic NaZn₁₃ crystal structure. As indicated by the magnetic measurement, the most significant magnetic entropy change |∆S_M(T)| of the sample decreased from 28.92 J/kg·K to 4.22 J/kg·K with the increase of the Co content under the 0–1.5 T magnetic field, while the Curie temperature T_C increased from 185 K to the room temperature 296 K, which indicated that this series of alloys are the room temperature magnetic refrigerant material with practical value. By using the ferromagnetic Curie temperature theory and analyzing the effect of Co doping on the exchange integral of these alloys, the mechanism that the Curie temperature of La_0.5Pr_0.5(Fe_1−xCo_x)_11.4Si_1.6 and La_0.8Ce_0.2(Fe_1−xCo_x)_11.4Si_1.6 increased with the increase in the Co content was reasonably explained. Accordingly, this paper can provide a theoretical reference for subsequent studies.     

Magnetic and Magnetostrictive Behaviors of Laves-Phase Rare-Earth—Transition-Metal Compounds Tb1−xDyxCo1.95

The magnetic morphotropic phase boundary (MPB) was first discovered in Laves-phase magnetoelastic system Tb–Dy–Co alloys (PRL 104, 197201 (2010)). However, the composition-dependent and temperature-dependent magnetostrictive behavior for this system, which is crucial to both practical application and the understanding of transitions across the MPB, is still lacking. In this work, the composition-dependence and temperature-dependence of magnetostriction for Tb_1−xDy_xCo_1.95 (x = 0.3~0.8) are presented. In a ferrimagnetic state (as selected 100 K in the present work), the near-MPB compositions x = 0.6 and 0.7, exhibit the largest saturation magnetization M_S and the lowest coercive field H_C; by contrast, the off-MPB composition x = 0.5, exhibits the largest magnetostriction, the lowest M_S, and the largest H_C. Besides, a sign change of magnetostriction is observed, which occurs with the magnetic transition across the MPB. Our results suggest the combining effect from the lattice strain induced from structure phase transition, and the influence of the MPB on magnetocrystalline anisotropy. This work may stimulate the research interests on the transition behavior around the MPB and its relationship with physical properties, and also provide guidance in designing high-performance magnetostrictive materials for practical applications.     

Investigation of Mechanical and Magnetic Properties of Co-Based Amorphous Powders Obtained by Atomization

Properties of Co-based alloys with high Glass Forming Ability (GFA) in the form of powder are still not widely known. However, powders of high GFA alloys are often used for the development of bulk metallic glasses by additive manufacturing. In this work Co_47.6B_21.9Fe_20.4Si_5.1Nb₅% at. and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁% at. were developed by gas-atomization. Obtained powders in size 50–80 µm were annealed at T_g and T_x of each alloy. Then SEM observation, EDS analyses, differential thermal analysis, X-ray diffraction, nanoindentation, Mössbauer, and magnetic properties research was carried out for as-atomized and annealed states. The gas atomization method proved to be an efficient method for manufacturing Co-based metallic glasses. The obtained powder particles were spherical and chemically homogeneous. Annealing resulted in an increase of mechanical properties such as hardness and the elastic module of Co_47.6B_21.9Fe_20.4Si_5.1Nb₅% at and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁%, which was caused by crystallization. The magnetic study shows that Co_47.6B_21.9Fe_20.4Si_5.1Nb₅ and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁ are soft magnetic and semi-hard magnetic materials, respectively.     

Phase Formation,Microstructure, and Magnetic Properties of Nd14.5Fe79.3B6.2 Melt-Spun Ribbons with Different Ce and Y Substitutions

Phase formation and microstructure of (Nd_1-2xCe_xY_x)_14.5Fe_79.3B_6.2 (x = 0.05, 0.10, 0.15, 0.20, 0.25) alloys were studied experimentally. The results reveal that (Nd_1-2xCe_xY_x)_14.5Fe_79.3B_6.2 annealed alloys show (NdCeY)₂Fe₁₄B phase with the tetragonal Nd₂Fe₁₄B-typed structure (space group P4₂/mnm) and rich-RE (α-Nd) phase, while (Nd_1-2xCe_xY_x)_14.5Fe_79.3B_6.2 ribbons prepared by melt-spun technology are composed of (NdCeY)₂Fe₁₄B phase, α-Nd phase and α-Fe phase, except for the ribbon with x = 0.25, which consists of additional CeFe₂ phase. On the other hand, magnetic properties of (Nd_1-2xCe_xY_x)_14.5Fe_79.3B_6.2 melt-spun ribbons were measured by a vibrating sample magnetometer (VSM). The measured results show that the remanence (B_r) and the coercivity (H_cj) of the melt-spun ribbons decrease with the increase of Ce and Y substitutions, while the maximum magnetic energy product ((BH)_max) of the ribbons decreases and then increases. The tendency of magnetic properties of the ribbons could result from the co-substitution of Ce and Y for Nd in Nd₂Fe₁₄B phase and different phase constitutions. It was found that the H_cj of the ribbon with x = 0.20 is relatively high to be 9.01 kOe, while the (BH)_max of the ribbon with x = 0.25 still reaches to be 9.06 MGOe. It suggests that magnetic properties of Nd-Fe-B ribbons with Ce and Y co-substitution could be tunable through alloy composition and phase formation to fabricate novel Nd-Fe-B magnets with low costs and high performance.     

Structure and Magnetic Properties of Thermodynamically Predicted Rapidly Quenched Fe85-xCuxB15 Alloys

In this work, based on the thermodynamic prediction, the comprehensive studies of the influence of Cu for Fe substitution on the crystal structure and magnetic properties of the rapidly quenched Fe₈₅B₁₅ alloy in the ribbon form are performed. Using thermodynamic calculations, the parabolic shape dependence of the ΔG^amoprh with a minimum value at 0.6% of Cu was predicted. The ΔG^amoprh from the Cu content dependence shape is also asymmetric, and, for Cu = 0% and Cu = 1.5%, the same ΔG^amoprh value is observed. The heat treatment optimization process of all alloys showed that the least lossy (with a minimum value of core power losses) is the nanocomposite state of nanocrystals immersed in an amorphous matrix obtained by annealing in the temperature range of 300–330 °C for 20 min. The minimum value of core power losses P_10/50 (core power losses at 1T@50Hz) of optimally annealed Fe_85-xCu_xB₁₅ x = 0,0.6,1.2% alloys come from completely different crystallization states of nanocomposite materials, but it strongly correlates with Cu content and, thus, a number of nucleation sites. The TEM observations showed that, for the Cu-free alloy, the least lossy crystal structure is related to 2–3 nm short-ordered clusters; for the Cu = 0.6% alloy, only the limited value of several α-Fe nanograins are found, while for the Cu-rich alloy with Cu = 1.2%, the average diameter of nanograins is about 26 nm, and they are randomly distributed in the amorphous matrix. The only high number of nucleation sites in the Cu = 1.2% alloy allows for a sufficient level of grains’ coarsening of the α-Fe phase that strongly enhances the ferromagnetic exchange between the α-Fe nanocrystals, which is clearly seen with the increasing value of saturation induction up to 1.7T. The air-annealing process tested on studied alloys for optimal annealing conditions proves the possibility of its use for this type of material.     

Some Thermomagnetic and Mechanical Properties of Amorphous Fe75Zr4Ti3Cu1B17 Ribbons

The microstructure, revealed by X-ray diffraction and transmission Mössbauer spectroscopy, magnetization versus temperature, external magnetizing field induction and mechanical hardness of the as-quenched Fe₇₅Zr₄Ti₃Cu₁B₁₇ amorphous alloy with two refractory metals (Zr, Ti) have been measured. The X-ray diffraction is consistent with the Mössbauer spectra and is characteristic of a single-phase amorphous ferromagnet. The Curie point of the alloy is about 455 K, and the peak value of the isothermal magnetic entropy change, derived from the magnetization versus external magnetizing field induction curves, equals 1.7 J·kg⁻¹·K⁻¹. The refrigerant capacity of this alloy exhibits the linear dependence on the maximum magnetizing induction (B_m) and reaches a value of 110 J·kg⁻¹ at B_m = 2 T. The average value of the instrumental hardness (HV_IT) is about 14.5 GPa and is superior to other crystalline Fe-based metallic materials measured under the same conditions. HV_IT does not change drastically, and the only statistically acceptable changes are visibly proving the single-phase character of the material.     

Study of Bulk Amorphous and Nanocrystalline Alloys Fabricated by High-Sphericity Fe84Si7B5C2Cr2 Amorphous Powders at Different Spark-Plasma-Sintering Temperatures

The new generation of high-frequency and high-efficiency motors has high demands on the soft magnetic properties, mechanical properties and corrosion resistance of its core materials. Bulk amorphous and nanocrystalline alloys not only meet its performance requirements but also conform to the current technical concept of integrated forming. At present, spark plasma sintering (SPS) is expected to break through the cooling-capacity limitation of traditional casting technology with high possibility to fabricate bulk metallic glasses (BMGs). In this study, Fe₈₄Si₇B₅C₂Cr₂ soft magnetic amorphous powders with high sphericity were prepared by a new atomization technology, and its characteristic temperature was measured by DSC to determine the SPS temperature. The SEM, XRD, VSM and universal testing machine were used to analyze the compacts at different sintering temperatures. The results show that the powders cannot be consolidated by cold pressing (50 and 500 MPa) or SPS temperature below 753 K (glass transition temperature T_g = 767 K), and the tap density is only 4.46 g·cm⁻³. When SPS temperature reached above 773 K, however, the compact could be prepared smoothly, and the density, saturation magnetization, coercivity and compressive strength of the compacts increased with the elevated sintering temperature. In addition, due to superheating, crystallization occurred even when the sintering temperature was lower than 829 K (with the first crystallization onset temperature being T_x1 = 829 K). The compact was almost completely crystallized at 813 K, resulting in a sharp increase in the coercivity of the compact from 55.55 A·m⁻¹ at 793 K to 443.17 A·m⁻¹. It is noted that the nanocrystals kept growing in size as the temperature increased to 833 K, which increased the coercivity remarkably but showed an enhanced saturation magnetization.     

Annealing Effect on the Characteristics of Co40Fe40W10B10 Thin Films on Si(100) Substrate

This research explores the behavior of Co₄₀Fe₄₀W₁₀B₁₀ when it is sputtered onto Si(100) substrates with a thickness (t_f) ranging from 10 nm to 100 nm, and then altered by an annealing process at temperatures of 200 °C, 250 °C, 300 °C, and 350 °C, respectively. The crystal structure and grain size of Co₄₀Fe₄₀W₁₀B₁₀ films with different thicknesses and annealing temperatures are observed and estimated by an X-ray diffractometer pattern (XRD) and full-width at half maximum (FWHM). The XRD of annealing Co₄₀Fe₄₀W₁₀B₁₀ films at 200 °C exhibited an amorphous status due to insufficient heating drive force. Moreover, the thicknesses and annealing temperatures of body-centered cubic (BCC) CoFe (110) peaks were detected when annealing at 250 °C with thicknesses ranging from 80 nm to 100 nm, annealing at 300 °C with thicknesses ranging from 50 nm to 100 nm, and annealing at 350 °C with thicknesses ranging from 10 nm to 100 nm. The FWHM of CoFe (110) decreased and the grain size increased when the thickness and annealing temperature increased. The CoFe (110) peak revealed magnetocrystalline anisotropy, which was related to strong low-frequency alternative-current magnetic susceptibility (χ_ac) and induced an increasing trend in saturation magnetization (Ms) as the thickness and annealing temperature increased. The contact angles of all Co₄₀Fe₄₀W₁₀B₁₀ films were less than 90°, indicating the hydrophilic nature of Co₄₀Fe₄₀W₁₀B₁₀ films. Furthermore, the surface energy of Co₄₀Fe₄₀W₁₀B₁₀ presented an increased trend as the thickness and annealing temperature increased. According to the results, the optimal conditions are a thickness of 100 nm and an annealing temperature of 350 °C, owing to high χ_ac, large Ms, and strong adhesion; this indicates that annealing Co₄₀Fe₄₀W₁₀B₁₀ at 350 °C and with a thickness of 100 nm exhibits good thermal stability and can become a free or pinned layer in a magnetic tunneling junction (MTJ) application.     

The Effect of Cobalt-Sublattice Disorder on Spin Polarisation in Co2FexMn1?xSi Heusler Alloys

In this work we present a theoretical study of the effect of disorder on spin polarisation at the Fermi level, and the disorder formation energies for Co₂Fe_xMn_1−xSi (CFMS) alloys. The electronic calculations are based on density functional theory with a Hubbard U term. Chemical disorders studied consist of swapping Co with Fe/Mn and Co with Si; in all cases we found these are detrimental for spin polarisation, i.e., the spin polarisation not only decreases in magnitude, but also can change sign depending on the particular disorder. Formation energy calculation shows that Co–Si disorder has higher energies of formation in CFMS compared to Co₂MnSi and Co₂FeSi, with maximum values occurring for x in the range 0.5–0.75. Cross-sectional structural studies of reference Co₂MnSi, Co₂Fe_0.5Mn_0.5Si, and Co₂FeSi by Z-contrast scanning transmission electron microscopy are in qualitative agreement with total energy calculations of the disordered structures.     

Influence of the Nb and V Addition on the Microstructure and Corrosion Resistance of the Fe-B-Co-Si Alloy

The paper presents a comparison of the results of the corrosion resistance for three Fe-B-Co-Si-based newly developed alloys with the addition of Nb and V. The corrosion performance differences and microstructure variations were systematically studied using scanning electron microscope, electric corrosion equipment, X-ray diffractometer, and differential calorimeter. It has been shown that each alloying addition increased the corrosion resistance. The highest corrosion resistance obtained by potentiodynamic polarization was found for the alloy with both Nb and V addons (Fe₅₇Co₁₀B₂₀Si₅Nb₄V₄) and lowest in the case of the basic four-element Fe₆₂Co₁₅B₁₄Si₉ material. This shows that the proper choice of additions is of significant influence on the final performance of the alloy and allows tailoring of the material for specific applications.