Correlation between the optical properties of surface layers and bulk characteristics of amorphous alloys

Spectral ellipsometry was used to study surface layers of Fe₈₀ A ₅B₁₅ (A = Ti, V, Cr, Mn, Fe, Co, Ni) and Fe_78-x Ni_xSi₉B₁₃ (x = 0, 1, 4, 8, 16, 21 at. %) amorphous metal alloys obtained by melt spinning. The optical characteristics of the alloys were determined by solving the inverse problem of ellipsometry. A correlation between the optical properties of the surface layers of amorphous alloys and their thermal stability was found.     

Thermal neutron irradiation of Fe−Si−B glasses

Effect of thermal neutron irradiation of metallic glasses Fe₇₈Si₉B₁₃ and Fe₇₈Si₈B₁₄ has been studied using Mossbauer spectroscopy. The surfaces of the two specimens are found to behave very differently under irradiation. The difference may be attributed to the presence of a thin oxide layer at the surface of as-prepared Fe₇₈Si₉B₁₃.     

Onset of magnetism in concentrated ternary alloys I

The onset of magnetism and the magnetic propreties of concentrated substitutional ternary alloys A(Fe_1?xB_x)₂ (A = Y, Zr, U; B = Mn, Co, Ni and Al), Y₂(Ni_1?xCo_x)₇, Y(Ni_1?xCo_x)₃, Y₆(Fe_1?xMn_x)₂₃ and Ti(Fe_1?xCo_x) as well as the amorphous alloy system (Fe_1?xNi_x)₇₇Si₁₀B₁₃ are discussed in terms of homogeneous and heterogeneous models based on the Stoner-, Edwards- Wohlfa arth- and the Landau theory of phase transitions of second order. For a detailed comparison of the nine ternary systems A(Fe, B)₂ (A = Y, Zr, U; B = Mn, Co, Al) we refer to a following paper. From the results obtained on alloying UNi₂ with Fe, Co and Cu we propose that the magnetic moment of UNi₂—contrary to UFe₂—resides mainly on U rather than on the Ni site. The appearance of magnetism in YNi_x compounds by either changing the Y : Ni ratio or substituting Ni by Co in YNi₃ and Y₂Ni₇ is mainly attributed to band effects for which a schematic N(E) curve is proposed. The breakdown of long-range magnetic order in Y₆(Fe, Mn)₂₃ seems to be caused by a lack of delocalized electrons and a preferential site occupation of Mn and Fe. The magnetic properties of Ti(Fe_1?xCo_x) change from an itinerant to a localized moment behaviour above and below x = 0.5 due to the occurrence of Fe antistructure atoms which drive the onset of long-range magnetic order. The occurrence of magnetism in amorphous alloys compared with that of crystalline alloys with a high degree of disorder may be characterized in a similar way.     

Etude De La Conductivite Electrique Des Ferrites Oxyfluores A Structure Spinelle

An investigation of the electrical conductivity of some oxyfluoride spinels of formula Zn_x²⁺Fe_1?x³⁺[M²⁺ Fe³⁺]O_4?xF_x (M = Fe, Co, Ni) and Fe³⁺[N_x²⁺Fe²⁺Fe_1?x³⁺]O_4?xF_x (N = Fe, Ni) shows that the conduction depends on the composition of the B sites: the activation energy increases, the conductivity and the Fe₃O₄ transition temperature decrease as the substitution rate of Fe³⁺ by N²⁺ in the B sites increases. The authors conclude to a hopping mechanism between the B cations; the anionic sublattice and the cationic A sublattice do not participate in the conduction.     

Resistivity and magnetoresistance of Fe80B20 and Fe78B13Si9 amorphous glasses

Summary The electrical resistivity of Fe₈₀B₂₀ and Fe₇₈B₁₃Si₉ amorphous glasses as a function of temperature from 293 K down to 15 K was measured, and it was found to fit quite well with the model given by Cote and Meisel. Comparison between our resistivity measurements of Fe₈₀B₂₀ and others was made, where some differences were found. These resistivity differences are evidence for a variety of amorphous atomic arrangements of the samples. The longitudinal magnetoresistance of Fe₈₀B₂₀ and Fe₇₈B₁₃Si₉ at 293K and 77K was measured in a low magnetic field. The observed magnetoresistance shows a typical field dependence known for ferromagnetic materials.     

Structural and magnetic study of bulk glassy Fe72 − x Co x B20Si4Nb4 alloys

The influence of the partial replacement of Fe by Co on the structural and magnetic properties of bulk-type glassy Fe_72???x Co _x B₂₀Si₄Nb₄ (x = 0, 5, 10, 15, 20, 25, 30, 35) alloys has been studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD) magnetic measurements and Mössbauer spectroscopy. Results show that the successive Co addition: (1) does not affect the mass density of the studied alloys, (2) affects appreciably the super cooled region, (3) modifies the magnetic properties, exhibiting soft magnetic behavior, (4) modifies the spin texture and disorder within the studied specimens.     

Vickers Microhardness and Hyperfine Magnetic Field Variations of Heat Treated Amorphous Fe78Si9B13 Alloy Ribbons

Amorphous Fe₇₈Si₉B₁₃ alloy ribbons were heat treated between 296 and 763 K, using heating rates between 1 and 4.5 K/min. Whereas one ribbon partially crystallized at T _x = 722 K, the other one partially crystallized at T _x = 763 K. The partially crystallized ribbon at 722 K, heat treated using a triangular form for the heating and cooling rates, was substantially less fragile than the partially crystallized at 763 K where a tooth saw form for the heating and cooling rates was used. Vickers microhardness and hyperfine magnetic field values behaved almost concomitantly between 296 and 673 K. The Mössbauer spectral line widths of the heat-treated ribbons decreased continuously from 296 to 500 K, suggesting stress relief in this temperature range where the Vickers microhardness did not increase. At 523 K the line width decreased further but the microhardness increased substantially. After 523 K the line width behave in an oscillating form as well as the microhardness, indicating other structural changes in addition to the stress relief. Finally, positron lifetime data showed that both inner part and surface of Fe₇₈Si₉B₁₃ alloy ribbons were affected distinctly. Variations on the surface may be the cause of some of the high Vickers microhardness values measured in the amorphous state.     

Permeability-frequency spectra of (Fe1−xcox)73.5Cu1Nb3Si13.5B9 nanocrystalline alloys under different magnetic fields

Under various amplitude of AC magnetic fields domain wall motion is the main mechanism in the magnetization process. This includes domain wall bulging and domain wall displacing. In this paper complex permeability-frequency spectra of (Fe_1−xCo_x)_73.5Cu₁Nb₃Si_13.5B₉ (x=0,0.5$x=0,0.5$) nanocrystalline alloys were measured as a function of the AC magnetic field, ranging from 0.001 to 0.04 Oe. Obvious changes have been found in complex permeability spectra for alloy x=0$x=0$ with the change of the amplitude of AC magnetic field, but variation of AC magnetic field has little effect on complex permeability spectra for alloy x=0.5$x=0.5$. This is attributed to the increased pinning field after substitution of Fe with Co in Fe_73.5Cu₁Nb₃Si_13.5B₉ nanaocrystalline alloy.     

Investigation of X-ray diffraction and positron life times in Fe78Si9B13 alloys of amorphous and crystalline structures before and after hydriding

Measurements of mean positron life-times and X-ray diffraction were carried out in unhydrided alloys Fe₇₈Si₉B₁₃ of amorphous and crystalline structures, and after hydriding them. The process of hydriding was carried out at a pressure of 55.773 × 10⁵ N/m². during 168 h. The crystalline samples were obtained after annealing the amorphous alloy Fe₇₈Si₉B₁₃ at 673, 773 and 873 K, respectively. The results obtained after the hydriding process suggest thatan additional electron energy band is formed due to introducing hydrogen inside the samples. The annealing process shows that there exists a nonmonotonic relation between the concentration of free electrons and the degree of order to the structure.     

Amorphous FexCo78-xSi9B13 alloys in radio frequency fields

The “rf collapse” effect is used to determine the quadrupole splitting distributions in ferromagnetic amorphous Fe_xCo_78-xSi₉B₁₃ alloys. The rf field induces crystallization of amorphous alloys which, for x<60 at.%, suppress the rf collapse.     

Structure of α-FeSi alloys with 8 and 10 at % silicon

The atomic structure of single-crystal samples of Fe_{1 ? x} Si _x (x = 0.08, 0.10) alloys has been investigated using X-ray diffraction. It has been shown that the body-centered cubic (BCC) lattice of these alloys contain clusters with local ordering of the B2 type, which are characteristic of alloys with depleted composition (x = 0.05?0.06). The Fe₃Si phase with the D0₃ structure has been revealed at silicon concentrations x = 0.08 and 0.10. The volume fraction of Fe₃Si-phase regions increases both with an increase in the silicon concentration in the Fe_{1 ? x} Si _x alloy and during annealing of the samples with this silicon concentration at a temperature of 450°C. Based on the results obtained, it has been concluded that the anisotropic distribution of the B2 clusters, which arises as a result of thermomagnetic or thermomechanical treatment, is responsible for the induction and stability of the uniaxial magnetic anisotropy in the Fe_{1 ? x} Si _x (x = 0.05?0.10) alloys.     

Disaccomodation phenomenon in Fe82B18-xCx and Fe82B18-xSix metallic glasses

The isochronal disaccomodation (DA) of the initial permeability was measured in Fe₈₂B_18-xC_x and Fe₈₂B_18-xSi_x metallic glasses in the temperature range from 77 to 600 K. An asymmetric isochronal spectrum with a single relaxation peak was observed on each studied glassy alloy. The peak shifts to the lower temperature side with increasing C content in Fe₈₂B_18-xC_x, whereas the influence of Si on the peak in Fe₈₂B_18-xSi_x is opposite to the effect of C. The kinet ic behavior of DA was examined and the activation energy spectrum was evaluated. The replacement of B by C gives rise to the reduction of the activation energy, whereas the addition of Si increases the energy. A clearly annealing effect on DA was observed on each examined alloy.     

Stress-MI and domain studies in Co-based nanocrystalline ribbons

A systematic investigation of the influence of different types of annealing on the magnetoimpedance (MI) effect in melt-spun (Co_1−xFe_x)₈₉Zr₇B₄ [x=0, 0.025, 0.05] and (Co_0.88Fe_0.12)_78.4Nb_2.6Si₉B₉Al ribbons has been carried out in the frequency range 500 kHz-13 MHz and under dc magnetic fields (H_dc) up to 80 Oe. In the stress annealed ribbons, the strain-induced transverse anisotropy is seen to result in large MI. Magnetic domains were investigated in the ribbons through magnetic force microscopy.     

铁基非晶的低频脉冲磁场处理效应

对非晶合金Fe₇₈ Si₉ B₁₃进行了低频脉冲磁场处理，用穆斯堡尔谱学、透射电 镜等方法观察处理试样的微观结构变化.研究发现，当脉冲频率20—25Hz,磁场16—32kA/m,作用时间≤2min，合金发生了纳米晶化，纳米相岐睩e(Si)晶粒尺寸为10nm. 而且，在低频脉冲磁场处理过程中，非晶试样的温升≤20℃. 关键词： 非晶态合金 脉冲磁场处理 纳米晶化     

Magnetic properties of metallic glasses based on Fe−Cr from Mössbauer spectroscopy

Spectra of metallic foils Fe_80?x Cr _x B₂ (x=6, 10, 15, 20) and Fe₆₀Cr₂₀B₁₂Si₈ were measured at range 4.2 K–300 K. Mössbauer data were analysed by Window’s Hesse-Rübartsch’s and Janot’s methods. The influence of the temperature and the Cr-content is discussed. The coefficientB _3/2 in Bloch’s law was calculated. Curie and crystallization temperature were taken from the DTA-DTMG method [1]. For finding the Curie temperature of the sample Fe₆₀Cr₂₀B₂₀ we used ac susceptibility, but this sample is not homogeneous.     

Nanocrystallization process and ferromagnetic properties of amorphous (Fe0.99Mo0.01)78Si9B13 ribbons

The nanocrystallization process of soft ferromagnetic (Fe_0.99Mo_0.01)₇₈Si₉B₁₃ ribbons has been studied in detail. Microstructural and ferromagnetic properties are examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), differential scanning calorimetry (DSC) and magnetization measurements. The Curie and crystallization temperatures are determined to be T_C=665 K and T_x=750 K, respectively. The T_x value is in well agreement with DSC measurement results. XRD patterns had shown two metastable phases (Fe₂₃B₆, Fe₃B) which were formed under in situ nanocrystallization process. These metastable phases embedded in the amorphous matrix have a significant effect on magnetic ordering. The ultimate nanocrystalline (NC) phases of α-Fe(Mo, Si) and Fe₂B at optimum annealing temperature had been observed respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of NC ferromagnetism, which suggest the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.     

Magnetostriction characteristics of the iron rich Fe-B-Si metallic glasses

Linear longitudinal and transverse magnetostriction and forced volume magnetostriction curves versus magnetic field for some as-quenched iron-rich amorphous alloys are presented. For the Fe₇₈Si₈B₁₄, Fe₇₈Si₉B₁₃ and Fe₇₉Si₁₂B₉ alloys the linear saturation magnetostriction was equal to 37·6×10^–6, 28·9×10^–8 and 34×10^–6, respectively.This work was in part financially supported by the Warsaw Technical University Institute of Material Science and Technology within the framework of the Project CPBR 2·4.     

非晶态(Fe1-xCox)78Si9.5B12.5合金的X射线光电子能谱研究

本文报道非晶态(Fe_1-xCo_x)₇₈Si_9.5B_12.5合金的X射线光电子能谱的实验结果,分别给出了Fe,Co,Si,B元素的内层电子能级的结合能以及费密面态密度随Co含量的变化关系。 关键词：     

Stoner excitations in the strong itinerant amorphous ferromagnets FexNi80−xB18Si2 and Fe80B20

Accurate measurements of the static magnetization of the amorphous ferromagnets Fe_xNi_80?xB₁₈Si₂ (x = 15, 20, 40, 60%) and Fe₈₀B₂₀ are reported. The results are analyzed in terms of spin-wave and Stoner excitations, and the latter indicate strong itinerant ferromagnetism with a Stoner gap Δ varying between 20 and 60 K. The other fitting parameters give values of the spin-wave stiffness and a quantity simply related to the saturation magnetization. The well-known anomaly regarding the spin-wave stiffness observed in earlier measurements in thus explained quantitatively.     

Limits of solubility,magnetic properties and electron concentration in Fe3-xTxSi system

The role of the outer electrons on the limits of solubility and bulk magnetic properties of the system Fe_3-xT_xSi (T - Ti, V, Cr, Mn, Co, Ni) is investigated. A correlation with the magnetic and structural behavior of Fe_1-cSi_c and Fe_1-cAl_c alloys is demonstrated.