Short-range ordering and crystallization of long-term melted Fe83P17 amorphous alloys

Mössbauer spectroscopy, X-ray diffractometry and DSC measurements were used to study the as-quenched state and the crystallization of Fe₈₃P₁₇ amorphous alloys quenched at several different cooling rates. The melt temperatures investigated were 1100 and 1250 °C. We have found changes in the hyperfine field distribution curves as a function of the quenching rate. These changes can be attributed to relaxation effects which are more considerable than those observed in Ni(Fe)P alloys. On the other hand, we have found differences in the phase composition of the partially crystallized alloys kept at different melt temperatures (but quenched at the same rate) at the same stage of crystallization. These can be associated with the similar effect of long-term melting as found earlier in Ni(Fe)P and FeB alloys. This effect can also be expected theoretically in the investigated temperature range.     

Calculation of the electrical resistivity of amorphous Sn-noble metal alloys

The absolute value and temperature dependence of the electrical resistivity of amorphous AuSn and CuSn alloys have been calculated on the basis of the generalized Faber-Ziman theory. The partial structure factors of the amorphous AuSn alloys were calculated for a modified microcrystallite model using the electron diffraction data for the average structure factor. The experimentally observed difference of the temperature dependence of the resistivity in the AuSn and the CuSn series is found to be largely due to the different atomic pseudopotentials for the noble metal component in these alloys.     

Superconducting properties of amorphous transition metal alloys

We have co-sputtered amorphous films of several Mo and W-based superconducting alloys. Measurements of T_c, ($\text{d}\text{H}{}_{\mathrm{c2}}\text{d}\text{T}$)_Tc and the normal state resistivity near T_c were made on a number of these alloys. Our results and other data from the literature are studied to examine the correlation between T_c and the dressed density of states at the Fermi level.     

Electronic structure of amorphous transition metal alloys

The electrical resistivity, the Hall coefficient and the magnetic susceptibility of amorphous alloys (Metglass 2826A, Allied Chemical) have been measured above room temperature. The experimental data show strong similarities with liquid alloys.     

Magnetostriction of transition metal substituted Co-based amorphous alloys

The effects of the substitutions of 3d-, 4d- and 5d-transition metals for silicon on magnetostriction of Co-based amorphous alloys have been investigated by measuring the tension dependence of anisotropy field in magnetic hysteresis loop. Fractional changes of the magnetostriction with transition metal solutes in Co-based amorphous alloys are qualitatively discussed in terms of the magnetic moment and coordination number, and classified into 3 types, i.e., positive, negative and complicated types, from a viewpoint of the contribution to magnetostriction.     

Electrical resistivity of amorphous alloys

Amorphous alloys of Ga, Sn, Pb and Bi with Cu, Ag and Au are produced by evaporation on a cold substrate. The residual resistivity, the temperature dependence of the resistivity, the transition temperature of superconductivity and the temperature of the amorphous-crystalline transformation are measured. We observe e.g. that the residual resistivity increases with the noble metal concentration, and that the temperature coefficient of the resistivity of the Au alloys is always negative. In these two respects amorphous alloys differ in behaviour from the corresponding liquid alloys. These observations can be correlated with the atomic energy levels of the free atoms.     

On the electrical resistivity of noble based transition metal dilute alloys

We apply the CPA expression of the electrical conductivity to the case of Au-based alloys containing 3d and 4d transition impurities. In this approach, a s-diagonal disorder larger for the 3d case than for the 4d one can explain the measured differences in resistivity between these two cases.     

Electrical resistivity of amorphous Sn-Cu alloys

The residual resistivity of amorphous Sn-Cu alloys increases with the Cu-concentration. Both positive and negative temperature coefficients are observed. The positive temperature coefficient and the transition temperature of superconductivity depend linearly on the Cu-concentration and both vanish simultaneously.     

Neutron diffraction study of Fe83B17 metallic glass

The structure factorS(Q) was measured up to high momentum transfer,_max720 nm^–1 for Fe₈₃B₁₇ metallic glass sample. A ribbon sample was prepared by rapid quenching of the melt. In the alloy boron enriched with¹¹B isotope was used. The scattering neutron spectra were measured by the time-of-flight method at the IBR-30 facility of JINR in Dubna. The scattering angles of 30°, 60° and 150° were chosen to cover the scattering vector,Q, from 10nm^–1 up to 720nm^–1. The scattered spectra of vanadium were measured for the detector efficiency determination and those of molybdenum for the calibration. The reduced pair distribution functionG(r) was obtained using the Fourier transform ofS(Q). The atomic distances and the partial coordination numbers were calculated. It was found that the fluctuation of the Fe-B distance is larger than that of the Fe-Fe atomic pair. The chemical short-range parameter is equal to 44% of the maximum possible value.Dedicated to the memory of M. Gmitro.The sample of amorphous metallic material was kindly prepared by Dr. P. Duhaj. We would like to thank Dr. P. vec for microscoping our sample and for stimulating discussions.     

Magneto-volume effect in invar-type amorphous Fe—B alloys

Amorphous Fe_100-xB_x(11.5 ≦ x ≦ 22) alloys having the invar characteristics were prepared by a single roller quenching method to investigate the magneto-volume effect. Forced volume magnetostriction, ?ω/?H, increased remarkably with decreasing boron content and the maximum value obtained was about 90 × 10^?10 Oe^?1 at 11.5 at.% boron. The estimated value of the pressure dependence of the Curie temperature, ?T_c/?P, was considerably large, being comparable to those of crystalline FeNi invar alloys. The ?T_c/?P curve plotted as a function of T_c approximately fitted Wohlfarth's expression.     

Composition dependence of the electrical transport properties of amorphous transition metal alloys

Summary A quadratic composition dependence of the electrical resistivity of amorphous transition metal alloys has been investigated at room temperature. A very good agreement between the theoretical and the observed values has been obtained in the case of Ni_xZr_1−x and Cu_xZr_1−x for all compositions. The thermoelectric power was then correlated with the electrical resistivity satisfactorily for the Cu_xZr_1−x and Ni_xZr_1−x To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Low-temperature crystallization of the Fe−Co−B amorphous alloys

Low-temperature crystallization of the melt-spun amorphous ribbon Fe₆₄Co₂₁B₁₅ was measured by the⁵⁷Fe Mössbauerin situ scanning method in the temperature range of about 300 to 350°C. Least-squares fit of the time-dependent α-Fe?Co isothermal absorption intensity revealed up to three superimposed exponential processes. Taking into account that this method indicates the content of the crystallized metallic phase only, then the first two (nucleation and primary crystallization) processes are followed by a rather slow third one, which could only mean the decay of metastable (Fe, Co)₃B having a thermally activated character as well. Besides confirming the previously reported activation enthalpies for the two faster processes, that of the slowest one was determined as (450±10) kJ/mol.     

Crystallization kinetics of the Fe−Co−B amorphous alloys

A series of amorphous ribbons Fe_85−x Co _x B₁₅ was subjected to the isothermal crystallization annealing. The alloys forx=12, 15, 17, 19, 21, 23, and 25 at.% Co were measured at room temperature by standard transmission technique during interrupted annealing. The samples with 12 and 21 at.% Co were used for direct scanning at constant velocity of the outermost metallic peak. In both cases gradually increasing content of the metallic Fe−Co phase was observed in at least two stages. Several scanning temperatures applied with the 12 and 21 at.% Co samples made it possible to draw the Arrhenius plots and to estimate the activation enthalpies of the processes. By analysing the Avrami exponents and activation enthalpies, the first process is attributed to a comparatively fast primary Fe−Co crystallization followed by the transformations of the amorphous rest.     

On the concentration dependence of transport coefficients in amorphous transition metal alloys

We discuss the concentration dependence of resistivity of CuTM (TM  Ti, Zr, Hf) amorphous alloys within a framework of a two-band model in which the s-states dominate conduction at the Cu end while the conduction of the d-states becomes increasingly important at TM rich end. We present a simple empirical relation that well describes the concentration dependence of the Hall coefficient and its sign reversal.     

Crystallization kinetics of amorphous FeB alloys by dta

The crystallization kinetics of amorphous FeB alloys was investigated by means of differential thermal analysis. The activation energy for the crystallization of amorphous FeB alloys was estimated. The concentration dependence of the activation energy, exhibiting a maximum at about 16 at.% B, has similarity to other physical properties.     

Superconductivity and resistivity of amorphous niobium-germanium alloys

The superconducting transition temperature, T_c, and the normal state resistivity, π, for amorphous niobium-germanium alloys were shown to vary smoothly with composition. Most notably, no anomaly was observed in the amorphous state at the composition Nb₃Ge.     

On the resistivity minimum in amorphous ferromagnetic alloys

We present a theoretical approach which, taking into account the amorphous nature of the system and the correlations between nearest-neighbour magnetic ions, gives a plausible explanation of some features present in the electrical resistivity of amorphous ferromagnetic alloys with transition metals.