Ball milling of Fe40Ni40P20-xSix (x = 6, 10 and 14): production and characterization

Progress in the ball milling amorphization of elemental powders with the overall composition Fe₄₀Ni₄₀P_{20 ? x}Si_x (X = 6, 10 and 14) and thermally induced crystallization of obtained alloys were characterized by differential scanning calorimetry, X-ray diffraction and transmission Mössbauer spectroscopy (TMS). Diffusion of Si into Fe and Ni alloys promotes the formation of the amorphous phase, via previous formation of (Fe, Ni) phosphides. After milling for 32–64 h, most of the powders are amorphous but bcc Fe(Si) crystallites remain (about 5% in volume). TMS results indicate that homogenization of the amorphous phase occurs by interdiffusion of Ni and Fe in Fe(Si,P)-rich and Ni(Si,P)-rich zones respectively. Annealing induces structural relaxation of stresses induced by milling, growth of bcc Fe(Si) crystallites, precipitation of bcc Fe(Si) and fcc Ni–Fe, and minor phases of Ni-rich silicides and (Fe, Ni) phosphides. The main ferromagnetic phase is bcc Fe(Si) for Fe₄₀Ni₄₀P₁₀Si₁₀ powders obtained after milling for 32 h. However, it is fcc Fe–Ni for the same alloy after milling for 64 h. In the later powders, as well as for alloys with x = 6 and 14 milled for 32 h, the fcc Fe–Ni shows the Invar magnetic collapse.     

Effect of Co or Mn addition on the soft magnetic properties of amorphous Fe89−xZr11Bx (x=5, 10) alloy ribbons

The temperature and field dependent magnetic properties of melt-spun amorphous Fe_89−x−yZr₁₁B_x(Co,Mn)_y (x=5, 10 and 0≤y≤10) alloys in the temperature range 5-1200 K are reported. The Curie temperature and saturation magnetization at room temperature increase (decrease) almost linearly with Co (Mn) addition. With increasing Co concentration, the room temperature coercivity increases at the rate of 2.26 (0.28) A/m per at% for the x=5 (10) samples. The high-field magnetic susceptibility and local magnetic anisotropy decrease (increases) rapidly with increasing Co (Mn) concentration. The thermomagnetic curves show a marked increase in magnetization above 850 K corresponding to the crystallization of α-FeCo (α-Fe) phase in samples containing Co (Mn). The Curie temperature of the crystalline phase increases (remains same) with increasing Co (Mn) concentration with the formation of α-FeCo (α-Fe). Addition of Co up to 10 at% in Fe-Zr-B improves the room temperature saturation magnetization from 0.56 to 1.2 T, and Curie temperature from 315 to 476 K. Also, the coercivity increases with Co addition from 1.27 to 23.88 A/m for x=5 and from 7.64 to 10.35 A/m for x=10 alloy. The non-collinear spin structures that characterize Fe rich Fe-Zr-B amorphous alloys have been used to describe the observed results.     

Magnetic Properties of Amorphous and Nanocrystalline Fe-Zr-B-Al Alloys

We have investigated the influence of aluminium substitution for iron on the magnetic properties of amorphous and nanocrystalline Fe_88-x Zr₇B₅Al _x alloys (x = 0, 1, 3, 5, 7 and 9 at.%). Thermomagnetic curves show an increase of Curie and crystallization temperature of amorphous phase with the increase of the content of aluminium in the alloy. The increase of aluminium content up to 3 at.% Al does not cause the decrease of a saturation magnetization in the as-quenched sample. In addition, magnetostriction of the annealed alloys has been studied. Also, the increase of aluminium content in the alloy causes an increase of the magnetostriction constant.     

Impact of iron composition on the calculated electronic and magnetic properties of Fe3−xNixSi

ABSTRACT

The structural, electronic and magnetic properties of Fe_3?xNi_xSi alloys with variable iron composition (0?≤?x?≤?1) have been investigated within by using Projector augmented wave (PAW) method. The exchange–correlation potential was treated with the generalised gradient approximation (GGA) for the calculation of the structural properties and for the computation of the electronic and magnetic properties in order to treat the d states. These alloys crystallize in cubic Heusler structures; The Fe₃Si and Fe₂NiSi have a regular structure DO₃ and L2₁ respectively. To describe the experimental proprieties we use the on-site Coulomb interactions of U_eff(Ni)?=?3.1?eV and U_eff(Fe)?=?3.4?eV. A good agreement between calculated and experimental magnetic moments is found for the cubic Heusler phases without the addition of Hubbard-model. The obtained results of the density of states and the spin-polarized band structure show that the Fe₂NiSi alloy has half-metallic property. Through the obtained values of the total spin magnetic moment, we conclude that in general, the Fe₂NiSi alloy is half-metallic ferromagnet material whereas the Fe₃Si alloy has a metallic nature.     

In situ Mössbauer and magnetization studies of Fe–Si nanocrystallization in Fe73.5Si13.5B9Cu1Nb1 X2, with X = Nb, Zr, Mo, amorphous alloys

The Fe–Si nanosized particles were obtained by controlled partial crystallization of Fe_73.5Si_13.5B₉Cu₁Nb₁X₂ (X = Nb, Zr, Mo) amorphous alloys. In situ Mössbauer spectroscopy and magnetization measurements have been used to follow the temperature-dependent magnetization of the amorphous as well as of the nanosized Fe–Si particles. Our results, for the residual amorphous and of nanoparticles phases, show that the temperature dependence of the hyperfine field and magnetization of both residual amorphous and nanocrystalline Fe(Si) phases are different from that of the as-quenched bulk amorphous or crystalline Fe₃Si alloys. Likewise, from the temperature dependence studies it was possible to determine that the onset temperature of the nanocrystallization process increases in the sequence Mo < Nb < Zr, for the same annealing conditions.     

Structure,magnetic properties and magnetocaloric effects of Fe50Mn15−x Co x Ni35 alloys

Fe50Mn15-xCoxNi35(x=0,1,3,5,7)alloys were prepared by arc melting under purified argon atmosphere.The ingots were homogenized at 930°C for 90h followed by water quenching.The crystal structure,magnetic properties and magnetocaloric effects of the alloys were studied by X-ray diffraction(XRD)and MPMS-7-type SQUID.The results show that all samples still maintained a single-(Fe,Ni)-type phase structure.With the increase of the content of Co,the Curie temperatures of these alloys increased and exhibited a second-order magnetic transition from ferromagnetic(FM)to paramagnetic(PM)state near Curie temperature.The maximum magnetic entropy change and the relative cooling power of Fe50Mn10Co5Ni35alloy was 2.55 J/kg·K and 181 J/kg,respectively,for an external field change of 5T.Compared with rare earth metal Gd,Fe50Mn15-xCoxNi35 series of alloys have obvious advantage in resource price;their Curie temperatures can be tuned to near room temperature,maintain a relatively large magnetic entropy change at the same time and they are a type of potential magnetic refrigeration materials near room temperature.     

Kinetics of the nanocrystalline structure formation

The kinetics of the nanocrystalline structure formation in the Fe_73.5Cu₁Nb₃Si_22.5?xB_x (x=6. 7. 8. 9 at. %) was followed during the annealing runs interrupted between 300 and 700°C.⁵⁷Fe room temperature Mössbauer spectra were taken and complemented by the electrical resistivity and X-Ray diffraction measurements. It has been found that for the 50 K/min temperature increase the formation of the nanocrystalline phase begins above 450°C reaching a maximum around 500°C and is followed by the second stage of crystallization of the disordered intergranular remainder above ca 600°C accompanied by the changes in the occupation of the iron sites in the crystalline α?Fe?Si phase. Thus gained composition-temperature dependence seems to witness for the inhibiting influence of the substitution of B by Si on the crystallization process.     

Magnetic and electrical transport properties of amorphous Zr-Fe alloys

Amorphous Zr_1?xFe_x samples were prepared in the composition range 0.2 ? x ? 0.9 either by means of vapour deposition or melt spinning. The electrical resistivity was determined in the range 4.2–300 K. Negative temperature coefficients were observed in the whole concentration range. The extended Ziman theory (diffraction model) was found to be able to explain these results only if the effective valence of the Fe atoms involves not only s electrons but also d electrons. The magnetic properties and the ⁵⁷Fe Mössbauer effect of the Zr_1?xFe_x alloys were studied in the range 4.2–300 K. The Fe-rich alloys are ferromagnetic. The Fe moment vanishes in alloys of an Fe concentration lower than about 50 at%. In most alloys (x ? 0.8) the Curie temperature is below room temperature and continuously decreases with Zr concentration. By means of Mössbauer spectroscopy and magnetic measurements it is shown that compositional short-range order (CSRO) is present to a higher degree in melt-spun alloys than in vapour-deposited alloys. The effect of sign and magnitude of the heat of solution on CSRO and the magnetic properties is discussed.     

Strained and strain-relaxed epitaxial Ge1-xSnx alloys on Si（100） substrates

Epitaxial Ge1-xSnx alloys are grown separately on a Ge-buffer/Si(100) substrate and directly on a Si(100) substrate by molecular beam epitaxy (MBE) at low temperature. In the case of the Ge buffer/Si(100) substrate, a high crystalline quality strained Ge0.97Sn0.03 alloy is grown, with a χmin value of 6.7% measured by channeling and random Rutherford backscattering spectrometry (RBS), and a surface root-mean-square (RMS) roughness of 1.568 nm obtained by atomic force microscopy (AFM). In the case of the Si(100) substrate, strain-relaxed Ge0.97Sn0.03 alloys are epitaxially grown at 150°C-300°C, with the degree of strain relaxation being more than 96%. The X-ray diffraction (XRD) and AFM measurements demonstrate that the alloys each have a good crystalline quality and a relatively flat surface. The predominant defects accommodating the large misfit are Lomer edge dislocations at the interface, which are parallel to the interface plane and should not degrade electrical properties and device performance.     

Structure and magnetostriction of RFex (1.6 ? x ? 2.0) and R(Fe1−yTiy)1.8 (y ? 0.2) alloys (RDy0.65Tb0.25Pr0.1)

Structure, Curie temperature and magnetostriction of RFe_x (1.6 ? x ? 2.0) and R(Fe_1−yTi_y)_1.8 (y ? 0.2) alloys (RDy_0.65Tb_0.25Pr_0.1) have been investigated using optical microscopy, X-ray diffraction, AC initial susceptibility and standard strain gauge techniques. The homogenized RFe_x alloys are found to be essentially single phase in the range of 1.8 ? x ? 1.85. The second phase is a rare-earth-rich phase when x ? 1.8, and (Dy, Tb, Pr)Fe₃ phase when x ? 1.85. X-ray diffraction indicates that the R(Fe_1−yTi_y)_1.8 alloys contain a small amount of Fe₂Ti phase when y ? 0.05, which increases with the increment of Ti content. The Curie temperature of R(Fe₁−_yTi_y)_1.8 alloys slightly enhances with increasing Ti concentration when y ? 0.05, then remains almost unchanged in the range of 0.05 ? y ? 0.20. The magnetostriction of RFe_x alloys is improved when x ? 1.80 and reduced by increasing Fe content when x ? 1.85. The magnetostriction of R(Fe_1−yTi_y)_1.8 alloys is lowered by increasing Ti content.     

Fabrication of polycrystalline silicon films by Al‐induced crystallization of silicon‐rich oxide films

Polycrystalline silicon (poly‐Si) films were fabricated by aluminum (Al)‐induced crystallization of Si‐rich oxide (SiO_x) films. The fabrication was achieved by thermal annealing of SiO_x /Al bilayers below the eutectic temperature of the Al–Si alloy. The poly‐Si film resulting from SiO_1.45 exhibited good crystallinity with highly preferential (111) orientation, as deduced from Raman scattering, X‐ray diffraction, and transmission electron microscopy measurements. The poly‐Si film is probably formed by the Al‐induced layer exchange mechanism, which is mediated by Al oxide.     

Mg-Ni-Nd非晶合金晶化温度与晶化驱动力的预测

通过对Buschow提出的预测二元非晶态合金晶化温度的“最小空位”模型进行扩展,并进一步结合Miedema理论得到了一种预测三元非晶态合金晶化温度和晶化驱动力的理论方法.利用该方法计算了(Mg_70.6Ni_29.4)_1-xNd_{x(x＝5,10,15)非晶态合金的晶化温度、晶化驱动力以及晶化焓.其中晶化温度和晶化焓的理论预测值与实验值的相对误差分别小于8%和7%.同时发现较高的晶化驱动力会降低 关键词： 非晶态合金 晶化温度 晶化驱动力}     

On the determination of the volume fraction of the crystalline phase in amorphous-crystalline alloys

The possibility of determining volume fractions of crystalline and amorphous phases of partially crystalline alloys from X-ray diffraction data has been discussed. The crystallization of an amorphous microwire of the Fe_73.9B_13.2Si_10.9C₂ composition has been investigated. The crystallization leads to the formation of α-Fe and Fe(Si). An analysis has been made of the X-ray diffraction patterns recorded for a series of samples with different contents of the crystalline and amorphous phases. The angular range has been determined and the calibration graph has been constructed, which can be used to determine the volume fractions of the amorphous and crystalline components in amorphous-crystalline samples.     

Electrical and Magnetic Study of Bulk Amorphous Alloys Fe-Al-Ga-P-B-Si

Bulk amorphous alloys Fe-Al-Ga-P-B-Si were prepared by a single-roller melt spinning method. Electrical resistivity of alloys is of the order of 200 cm. The structural and magnetic components of resistivity are separated. The anomalous rise of resistivity during crystallization observed in Fe-Al-Ga-P-B-Si alloys with higher Si content is related to the precipitation of high resistivity crystalline phases. The strong exchange interaction is revealed by the Curie temperatures reaching 640 K. The room temperature values of the effective magnetic moment vary between 1.79 and 1.83 _B depending weakly on alloy composition. The AC hysteresis loops were recorded in magnetic fields up to 50 A/cm and frequencies between 10 Hz to 400 kHz. The frequency variation of power losses shows that high resistivity reduces eddy current losses.     

Enhancement in soft magnetic and ferromagnetic ordering behaviour through nanocrystallisation in Al substituted CoFeSiBNb alloys

The effect of substituting Al for Si in Co₃₆Fe₃₆Si_4−xAl_xB₂₀Nb₄, (X=0, 0.5, 1.0, 1.5, 2.0 at%) alloys prepared in the form of melt-spun ribbons have been investigated. All the alloys were amorphous in their as-cast state. The onset of crystallization as observed using differential scanning calorimetry (DSC) was found to rise at low Al content up to X=1 at% beyond which there was a decreasing trend. The alloys also exhibited glass transition at ‘T_g’. Microstructural studies of optimally annealed samples indicated finer dispersions of nanoparticles in amorphous matrix which were identified as bcc-(FeCo)Si and bcc-(FeCo)SiAl nanophases by X-ray diffraction technique. Alloy with optimum content of Al around X=1 at% exhibited stability in coercivity at elevated temperatures. Though Al addition is known to lower magnetostriction, such consistency in coercivity may also be attributed towards lowering in the nanoparticle size compared to X=0 alloy. In the nanostructured state, the alloy containing optimum Al content (X=1) exhibited further enhancement in ferromagnetic ordering or the Curie temperature by 100 K compared to alloy without Al. Such addition also attributed to better frequency response of coercivity and low core losses.     

Influence of composition on hyperfine interactions in FeMoCuB nanocrystalline alloy

Influence of varying Fe/B ratio upon hyperfine interactions is investigated in the Fe_91?x Mo₈Cu₁B_x rapidly quenched alloys. They are studied both in the as-quenched (amorphous) state as well as after one-hour annealing at different temperatures ranging from 330 °C up to 650 °C. Such a heat treatment causes significant structural changes featuring a formation of nanocrystalline bcc-Fe grains during the first crystallization step. At higher annealing temperatures, a grain growth of bcc-Fe and occurrence of additional crystalline phases are observed. The relative fraction of the crystalline phase governs the development of magnetic hyperfine fields in the residual amorphous matrix even if this was fully paramagnetic in the as-quenched state. The development of hyperfine interactions is discussed as a function of annealing temperature and composition of the investigated alloys. ⁵⁷Fe Mössbauer spectrometry was used as a principal analytical method. Additional information related to the structural arrangement is obtained from X-ray diffractometry. It is shown that in the as-quenched state, the relative fraction of magnetic hyperfine interactions increases as the amount of B rises. In partially crystalline samples, the contribution of magnetic hyperfine interactions inside the retained amorphous matrix increases with annealing temperature even though the relative fraction of amorphous magnetic regions decreases.     

Correlations between hyperfine parameters of Fe−Ni-B amorphous metals

The correlations between fluctuations in the⁵⁷Fe Mössbauer hyperfine parameters of the amorphous alloys (Fe_0.5Ni_0.5)_100?x B _x (x=16, 18, 20, 22 and 25 at%) and Fe_yNi_80?y B₂₀ (y=20, 25, 40 and 60 at%) have been determined. Values of the correlation between the fluctuations of the isomer shift and the fluctuations of magnetic hyperfine field, μ_N 〈ΔHΔδ〉 together with published values on similar amorphous systems are compared with correlation values for related crystalline phases. The lack of characteristic values suggests that the correlation values do not allow a link to be made between local structural units in amorphous alloy and crystalline phases.     

A potential Co36Fe36Si4B20Nb4 nanocrystalline alloy for high temperature soft magnetic applications

The paper addresses the structural, crystallization, soft magnetic and Curie temperature behaviour of Co₃₆Fe₃₆Si₄B₂₀Nb₄ alloy. The material, prepared in the form of ribbons by melt-spinning technique, was amorphous in the as-cast state. Differential scanning calorimetry (DSC) showed two stages of crystallization whereas thermal variation of electrical resistivity (TER) carried out to a higher range of temperature indicated three stages of crystallization. The first crystallization stage, which occurred at 845?K and 825?K in DSC and TER, respectively, was due to the formation of nanophase (CoFe)₂Si as evidenced by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The formation of these nanoparticles reduced the magnetocrystalline anisotropy, thereby revealing good soft magnetic properties in the samples annealed between 825?K and 875?K with coercivity less than 49.9?A?m^?1 (627?mOe) and susceptibility?～?0.72?×?10³. In this optimum nanocrystalline state, the material also exhibited a high Curie temperature above 1100?K, opening the scope of the present nanocrystalline alloy for high temperature applications.     

Structural and magnetic properties of electrospun FeCoNi magnetic nanofibers with nanogranular phases

Structural and magnetic properties of silicon/aluminum-added and -free FeCoNi magnetic alloy nanofibers with nanogranular phases prepared by electrospinning and subsequent annealing of the PVP-blended ternary metal precursors in hydrogen atmosphere were investigated. The FeCoNi magnetic alloy nanofibers with evenly distributed nanocrystalline phases were formed, which are identified as γ-Fe_1−x Ni _x binary phase with face-centered cubic structure and α-CoFe phase with body-centered cubic structure. At elevated temperature, the α → γ structural martensitic transformation in the FeCoNi ternary alloys occurred due to the inhomogeneities in composition of the matrix during annealing of the alloy with metastable α-phase. In the Si/Al-added FeCoNi nanofibers, more than two phases with complicated-boundaries of the grains in and/or outside the nanofibers were formed as crystalline phases and amorphous phase. The amorphous phase consisted of Si and/or Al acted as an inhibitor diminishing α → γ transformation as well as an interparticle insulation layer. At low annealing temperature of 450 °C, the Si/Al-added nanofiber mainly consisted of metastable α-phase with a low-crystallinity surface structure and very small diameter of 13 nm was formed and showed an unexpectedly high coercivity, which attributed to the surface effects and/or high surface/volume ratio.     

On the magnetic and crystallization behaviour of iron based amorphous alloys determined by nuclei quenched in

The tendency of boron-containing, iron-based glasses to show non monotonic changes of Curie Temperature (T _c ) and room temperature saturation magnetization (SM) was examined by magnetic measurements and Mossbauer spectroscopy. Depending on B/Fe ratio theT _c and SM first increased up to a maximum value and then steadily decreased, probably because of a shortrange ordering, due to the strong chemical interaction between iron and boron atoms, leading iron atoms in vicinity with Fe-atoms rather than another TM-atom. Finally, the phenomenon becomes analogous to the order-disorder phenomenon in crystalline alloys. An observed unusual crystallization behaviour, consisting of heterogeneous nucleation, was also ascribed to this ordering, which leads to the formation of associations, acting as the first nuclei of crystallization.