The pressure- and temperature dependence of the electrical resistivity of some amorphous Fe-B alloys

We report measurements of the electrical resistivity of the amorphous alloys Fe₄₀Ni₄₀P₁₄B₆ (Metglas 2826). Fe₃₂Ni₃₆Cr₁₄P₁₂B₆ (Metglas 2826A) Fe₈₀B₂₀ (Metglas 2605) and Fe₇₅B₂₅ as a function of pressure and temperature. The pressure is varied between 0 and 12 GPa, the temperature between 1.2 and 380 K. At low temperatures the pressure dependence yields additional information on the scattering mechanism.     

On the bimodality of the hyperfine field distribution in amorphous Fe32Ni36Cr14P12B6 alloy

The bimodality of the hyperfine field distribution in amorphous Fe₃₂Ni₃₆Cr₁₄P₁₂B₆ alloy reported by Chien et al. (Phys. Rev. B19 (1979) 81) is shown to be the result of the bimodality in the distribution of the values of the strengths of the bonds within the alloy. The bimodality in the distribution of the bond strength values arises from the presence of two types of dense random packed cells (one rich in Cr atoms and the other deficient in Cr) in the alloy.     

High-magnetic-field magnetization and magnetoresistance of some amorphous ferromagnets

Measurements of isothermal magnetization and magnetoresistance at T = 4.0-4.2 K and 15 ? H ? 132 kG on the amorphous ferromagnets Fe₈₀B₂₀, Fe₇₈Mo₂B₂₀, Fe₄₀Ni₄₀P₁₄B₆, and Fe₃₂Ni₃₆Cr₁₄P₁₂B₆ indicate a relatively large H-induced increase (3.6%) in the high-magnetic-field magnetization of the latter alloy, and marked differences in the magnitude and sign of the high-field magnetoresistance of the four alloys. The results are qualitatively interpreted in terms of internal effective field distributions which include a small fraction of atomic spins in negative field sites.     

Existence of both spin-glass and mictomagnetic behaviour in the amorphous Fe10Ni70P14B6 alloy

Results of the accurate magnetization measurements performed on the amorphous Fe₁₀Ni₇₀P₁₄B₆ alloy in the temperature range 20–77 K in fields upto 1 kOe are reported. The complex magnetic behaviour exhibited by this alloy has been analyzed to show that a ferromagnetic ordering, occuring on a localized microscopic scale at a temperature T₀ very close to that given by the earlier Hall effect measurements, is accompanied by a superparamagnetic behaviour which below T₀ causes at first a spin-glass freezing of the magnetic spins when they interact with one another on a long range scale and then a mictomagnetic freezing of the giant superparamagnetic clusters at a lower temperature as a result of exchange interaction between their moments and the frozen spin-glass matrix. In addition, the present results, besides providing a clear physical insight into the widely different ordering temperatures obtained for this alloy from previous Mössbauer and resistivity measurements, on one hand and from our magnetization measurements on the other, strongly suggest a magnetic origin for the observed resistivity-minimum phenomenon. In conclusion, the present alloy represents a composition in the amorphous (Fe_xNi_1?x)₈₀P₁₄B₆ system well below the percolation limit.     

Kinetics of induced magnetic directional order in a Fe40Ni40P14B6 amorphous alloy

The amorphous Fe₄₀Ni₄₀P₁₄B₆ alloy (Metglas 2826) has been annealed under magnetic field at several temperatures. The kinetics of induced magnetic anisotropy exhibits a broad spectrum (β = 4) of time constants; it obeys exactly an Arrhenius law with an activation energy of 1.74 ± 0.04 eV. These values are identical to those determined by resistivity measurements. This suggests the formation of short range directional order.     

Low temperature resistivities of FexNi80-xP14B6 metallic glasses

The resistivities of six Fe_xNi_80-xP₁₄B₆ alloys have been measured between 1.5 and 50 K. It is found that the resistivity variations both below and above the resistivity minima depend on the transition metal composition. The room temperature coefficients of the resistivity indicate the existence of the magnetic contribution to the resistivity.     

Transversal magnetic field effect on Fe40Ni40P14B6 amorphous alloys

A study about the influence of an electric current flowing through an amorphous ribbon Fe₄₀Ni₄₀P₁₄B₆ has been done. It has been found that the magnetization curves are strongly influenced by such a current (from 0 up to 5000 Hz). Bitter patterns under the action of the current have been observed in order to gain a better knowledge of these effects. The wall energy has been evaluated from a simple model.     

Mössbauer study of amorphous Fe40Ni40PxB20−x

The hyperfine field distributions of amorphous Fe₄₀Ni₄₀P_xB_20?x (x=10, 12, 14, 17) samples before and after different heat treatments have been determined by means of Mössbauer spectroscopy. All of these P(H) curves are characterized by a main high field maximum and an additional low field maximum, respectively. The asymmetry of distributions of high field component in P(H) of Fe₄₀Ni₄₀P_xB_20?x increases progressively from Fe₄₀Ni₄₀P₁₀B₁₀ to Fe₄₀Ni₄₀P₁₇B₃. The distributions of low field component in P(H) are affected differently by the annealing temperature. The results indicate that the phospoorus element plays an important role in the hyperfine interactions of amorphous Fe₄₀Ni₄₀P_xB_20?x The influence of annealing atmosphere has been discussed.     

Ni83Cr7Fe3Si4B3非晶态合金在常压及高压下的晶化过程

本文研究了Ni₈₃Cr₇Fe₃Si₄B₃非晶态合金在1bar及100kbar压力下的晶化过程,得到了“时间-温度-变态”图。其结果表明:经高压热处理后的非晶合金其晶化温度降低,fcc-Ni相区域加宽及亚稳Ⅱ相没有形成。另外,还分别计算了常压及100kbar压力下的晶化激活能。 关键词：     

Curie temperatures and crystallization behavior of amorphous Fe81−xNixZr7B12 (x=10, 20, 30, 40, 50, 60) alloys

Curie temperature, crystal structure and crystallization behavior of amorphous alloys with the stoichiometry Fe_81−xNi_xZr₇B₁₂ (x=10–60) have been studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and AC-magnetization (TMAG) measurements as functions of temperature. The thermal stability of long-range magnetic order, T_C vs. Ni content in as-quenched amorphous alloys exhibits maximum at 352 °C for x=40. The primary crystallization has been detected during annealing at the first crystallization stage of all ribbons investigated.     

Mössbauer study of magnetic anisotropy and structural relaxation in amorphous Fe40Ni40P x B20−x alloys

The amorphous Fe₄₀Ni₄₀P _x B_20?x (x=0, 10, 12, 14, 17) alloys before and after annealing have been studied by means of Mössbauer spectroscopy, etc. Heat treatment of various samples were performed at 225, 250, 275, 300, 325 and 350°C, respectively, for 1 h in a quartz tube in an argon atmosphere. The results show that the magnetic anisotropy and structural relaxation in amorphous Fe₄₀Ni₄₀P _x B_20?x are related to the phosphorus element concentrations involved and the annealing temperatures. A possible mechanism of two-stage relaxation processes below the glass transition temperature is discussed.     

Oxidation state and short range order at the surfaces of amorphous Fe40Ni40P14B6 ribbons

Conversion electron Mössbauer spectroscopy (CEMS) was used to study the oxidation state at the surfaces of amorphous Fe₄₀Ni₄₀P₁₄B₆ ribbons obtained by melt-spinning in air and vacuum heated at 583 K. Different concentrations of ferric and ferrous ions depend on the different behaviour of phosphorous diffusion towards the two surfaces during low annealing temperature.     

Electron transport properties of Co71−xFexCr7Si8B14 (x=0, 2, 3.2, 4, 6,8 and 12 at%) amorphous alloys during devitrification

The investigation addresses the electron transport properties of Co_71−xFe_xCr₇Si₈B₁₄ (x=0, 2, 3.2, 4, 6, 8 and 12 at%) amorphous alloys. The variation in electrical resistivity of as-cast amorphous materials with thermal scanning from room temperature to 1000 K was measured. The CoFe-based alloys revealed an initial decrease in temperature coefficient of resistivity (TCR), a characteristic of spin-wave phenomena in glassy metallic systems. This behaviour in the present alloys was in a sharp contrast to the Co-based amorphous materials that indicate the drop in resistivity much below room temperature. In the studied alloys, the variation in initial TCR values and the full-width at half-maxima determined from X-ray diffraction of as-quenched materials exhibited a similar trend with increasing Fe content, indicating the compositional effect of near neighbouring atoms. After the initial decrease in resistivity, all the alloys indicated a subsequent increase at T_min. The Curie temperature (T_C), which was measured from thermal variation of ac susceptibility showed non-monotonic change with Fe content. In the temperature range between T_min and T_C the relative scattering by electron-magnon and electron-phonon resulted in the non-monotonic change in Curie temperature. At crystallization onset (T_X1) all the alloys except there with X=6, showed a sharp decrease in electrical resistivity which was attributed to ordering phenomena. In contrast to this resistivity decrease, X=6 alloy exhibited a drastic increase in resistivity around T_X1 observed during amorphous to nanocrystalline transformation. Such nanocrystalline state was observed by Transmission electron microscopy.     

Stress-induced magnetic easy axis in amorphous Fe40Ni40P14B6

In a ribbon of amorphous Fe₄₀Ni₄₀P₁₄B₆ (Metglas 2826) the iron spins tend to be parallel to the plane of the ribbon, but the distribution of spin directions within the plane is nearly random. When a uniaxial tensile stress is applied to the ribbon the spins become almost completely aligned parallel to the applied stress. The technique of Mössbauer polarimetry was used to detect and measure this effect.     

Mössbauer study of the effect of preparation parameters in rapidly quenched Fe−Cr−P−C,Fe−Cr−B and Ni(57Fe)P amorphous alloys

Mössbauer spectroscopy was used to get information about the effect of preparation parameters (quenching rate, temperature and time of solution treatment of melt) on the structure of rapidly quenched Fe₇₀Cr₁₀C₇P₁₃, Fe₇₉Cr₁₅B₁₅ and Ni₈₀ ⁵⁷Fe₁P₁₉ amorphous alloys. We have found smaller but measurable thickness dependent changes in the average Mössbauer parameters and in the hyperfine field distribution of Fe₇₀Cr₁₀C₇P₁₃ samples than those observed in Fe₇₀Cr₁₀C₁₀P₁₀ amorphous alloys [3]. On the other hand, differences were found in the hyperfine field distribution of very rapidly quenched Fe₇₀Cr₁₀C₇P₁₃ alloys with increasing time of solution treatment of melt. Changes in the average parameters and in the quadrupole splitting distribution were also observed with variation of thickness as well as of temperature of melt in the Fe₇₀Cr₁₅B₁₅ and Ni₈₀(Fe)P₁₉ samples, respectively. The finding can be interpreted in terms of changes in the short range order due to different preparation conditions.     

X-ray absorption study of effective coordination charges of iron in crystals and amorphous solids

The positions of the K-absorption edges of iron are recorded for five crystals: Fe_0.885O, Fe_0.905O, Fe₃O₄, Fe₂O₃ and Fe metal, and for two amorphous solids: oxide glass ([Na₂O · 2SiO₂]_0.8 [Fe₂O₃]_0.2) and metallic glass (Fe₃₆Cr₃₂Ni₁₄P₁₂B₆). It is observed that there is a correlation between the positive X-ray K- absorption edge chemical shift and the effective coordination charge. The ionic state of iron in oxide glass is identical to the ferric iron in Fe₂O₃ as shown by the same positions of iron K-absorption edges in this glass and Fe₂O₃. The K-edge of the metallic glass appears 6.5 eV higher than that of the pure iron edge, which suggests that the bonding of iron in metallic glass is different from the pure iron metal.     

SAXS study of the structure of amorphous Fe75TM5B20 (TM  Ti,V, Cr,Mn, Fe,Co, Ni)

A SAXS study was undertaken on Fe₇₅TM₅B₂₀ amorphous alloys (TM  Ti, V, Cr, Mn, Fe, Co, Ni) to prove the effects of the substituting metals on structural homogeneity of the systems. A density-density correlation extending up to 20 Å belongs to Fe-, Ni- and Co-containing alloys whereas the absence of a medium-range order characterizes the texture of the remaining alloys. A net correspondence was found between these structural conditions and the isothermal behavior of the resistivity.     

Torque magnetometer measurements of the temperature dependence of induced anisotropy energy and of saturation magnetization in amorphous Fe40Ni40P14B6

Induced anisotropy energy K_u and saturation magnetization M have been measured as a function of temperature T between 77 K and T_c on co$\text{n}$venient specimens of amorphous Fe₄₀Ni₄₀P₁₄B₆ by means of a torque magnetometer. The M vs. T curve is found to follow an anomalously low behaviour with respect to crystalline materials. The exper$\text{i}$mental K_u vs. T curve is well fitted by a M² law, also different from higher power laws typical of crystalline alloys.     

57Fe Mössbauer study of amorphous Fe81B13.5Si3.5C2

The amorphous ferromagnet Fe₈₁B_13.5Si_3.5C₂ (Metglas^® 2605SC) has been investigated with Mössbauer spectroscopy. The hyperfine interaction parameters are studied between 80 and 300 K from which some characteristic properties are deduced. The behaviour of the amorphous alloy at higher temperatures has been studied by the room temperature spectra of annealed samples. After a structural relaxation process, a two step crystallization transformation is observed leading to Fe-Si alloy and Fe₂(B, C). X-ray diffraction of samples annealed at higher temperatures reveals the presence of an orthorhombic Fe-B-Si phase of which the structure changes slightly with annealing temperature.     

Electrical resistivity of amorphous metallic glasses Fe80B80 and Fe78Mo2B20 between 78 and 1000 K

Electrical resistivity (ρ) of amorphous Fe₈₀B₂₀ and Fe₇₈Mo₂B₂₀ have been studied as a function of temperature (T) between 78 and 1000 K. The ρ vs T curves, obtained with specified warming and cooling rates, show that such curves are sensitive probes of the crystallization process. Within the experimental error, no anomalies in the ρ behavior can be seen at the Curie temperature of each amorphous alloy.