Radiation-induced defects in amorphous Pd80Si20

Irradiation of the metallic glass Pd₈₀Si₂₀ with high energy Ar-ions at low temperatures resulted in electrical resistance increases of about 5% at a measuring temperature of 10 K after fluences of 3·10¹⁵ Ar/cm² indicating that defects were created by radiation damage. Annealing experiments were performed up to 150°C showing a smooth recovery throughout the whole temperature range.     

Structural evolution of nanocrystalline/amorphous Fe/Ni75B25 multilayers: temperature dependence of electrical resistivity

X-ray specular-reflectivity measurements have been carried out on nanocrystalline/amorphous Fe/Ni₇₅B₂₅ multilayer films which were sputter-deposited on Si substrates, to investigate the evolution of interface roughness and the correlation between structure and transport properties. A significant interface roughness correlation with increasing Fe/NiB layer repetition was observed. The investigated films indicated a temperature dependent high electrical resistivity—10⁴ μΩ-cm at 10 K and 10³ μΩ-cm at 300 K—with a semiconductor-metal transition like behavior. Selected area electron diffraction revealed the presence of crystalline bcc Fe phase and NiB in amorphous state. The structural and transport properties of the multilayers are discussed.     

Recovery of electrical resistivity in amorphous pdsi alloys after low temperature neutron irradiation

Measurements of electrical resistivity after low temperature fast neutron irradiation are made for amorphous Pd₈₀Si₂₀ and Pd₈₀Ni₂Sl₁₈ and then Pd₈₀Si₂₀ annealed at 230°C and 360°C, and the isochronal annealing curves are obtained. The resistivity increase of Pd₈₀Si₂₀ annealed at 360°C is about 10 times larger than that of amorphous alloys and no defined annealing stage is observed in amorphous alloys and Pd₈₀Si₂₀ annealed at 360°C. For amorphous Pd₈₀Si₂₀, about 60% of the resistivity increase by irradiation remains after annealing up to room temperature and these are discussed by the structural relaxation.     

Electrical resistance and magnetoresistance of amorphous alloys Gd67Co33 and Pd80Si20

In search for structural contributions to the low temperature anomaly we report high resolution resistance and magnetoresistance measurements ($\text{0.02}\text{K}\text{? T ? 20}\text{K}$) of amorphous splats of Gd₆₇Co₃₃ and Pd₈₀Si₂₀. For both alloys, the resistivity ?(H = 0, T) has a minimum at T ～ 10 K and increases with decreasing T. The ferromagnetic Gd₆₇Co₃₃ shows a strong negative field dependence of $\text{Δ?}\text{?(0)}$, saturating at H ～ 2T for T = 4.2 K but no measurable change in $\text{??}\text{?}\text{T}$ below 10 K is observed.The diamagnetic Pd₈₀Si₂₀ exhibits a positive field dependent magnetoresistance $\text{[Δ?}\text{?(0)]}\text{(}\text{H}\text{)}$ at low temperatures. Additionally, a field dependent part in $\text{??}\text{?}\text{T}$ is found which is probably due to paramagnetic impurities (～ 1 ppm Fe). However, there is also a field independent contribution in the amorphous state of Pd₈₀Si₂₀, which vanishes after crystallization. We attribute this to non-magnetic scattering induced by the disordered structure.     

Ultrasonic attenuation in superconducting Nb20Zr80

We have measured the low-temperature ultrasonic attenuation in quenched polycrystalline Nb₂₀Zr₈₀ at 30 and 90 MHz. The quenching process creates tunnelling states due to metastable regions of the athermal ω-phase. Our results can be explained on the basis of the interaction between electrons and tunnelling states.     

The low temperature heat capacity and electrical resistivity of ReO3

Low temperature heat capacity and electrical resistivity measurements are reported for ReO₃. The heat capacity data give an acoustical mode Debye temperature θ = 327 K, and an electrronic density of states parameter γ = 2.83 mJ/mole-K². The observed temperature dependence of the resistivity is consistent with the existence of electron scattering both from acoustic mode phonons and from optical mode phonons of characteristic temperature θ_E = 1080 K. The above measurements are used to evaluate the electron-phonon interaction parameter λ = 0.24.     

A simultaneous voltammetric and dilatometric study of hydrogen absorption in Pd and amorphous Pd80Si20

By simultaneously measuring the length change of a palladium electrode and the current through the electrolytical cell when a triangular voltage is applied across the cell, it is possible to distinguish between surface and bulk processes during hydrogen uptake in Pd. From a comparison of corresponding dilatograms and voltammograms of polycrystalline Pd with those of crystalline Pd and amorphous Pd₈₀Si₂₀, one concludes that the diffusion of hydrogen into the bulk of the samples takes place to a large extent along dislocation lines. Dilatometric and voltammetric measurements in magnetic fields up to 10T show that the absorption of well annealed Pd electrodes is increasing up to 1T and saturates at higher fields.     

Magnetic properties of amorphous Co75W25

Saturation magnetization M(T), spin wave stiffness D and Curie temperature T_c of amorphous Co₇₅W₂₅ were determined by magnetic measurements. Tungsten reduces these quantities more than metalloids or 3d-transition metals do. T_c is below room temperature. The ratio D/T_c, however, is equal to that observed on a fcc single crystal of Co₉₂Fe₈ and on amorphous Co-Ti alloys.     

Effect of pressure on the electrical resistivity of bulk Ge20Te80 glass

An irreversible pressure induced semiconductor-to-metal transition in bulk Ge₂₀Te₈₀ glass is observed at about 5 GPa pressure. The high pressure phase has a face centered cubic structure with a lattice constant 6.42 A° as deduced by X-ray diffraction studies on the pressure quenched samples. The temperature and pressure dependence of the electrical resistivity confirms the observed transition to be a semiconductor-to-metal transition. The temperature dependence of thermo electric power is also reported.     

The vibrational spectrum of Pd80Si20 metal glass

Inelastic neutron scattering can be used to measure the energy spectrum of the normal modes of vibration of a glass. We present measurements of the spectrum for the metal-metalloid glass Pd₈₀Si₂₀ at 300 K. They show a principal peak around 23 meV energy followed by a rapid fall. In these respects they closely resemble the known spectrum from crystalline pure palladium. We conclude that the inter-metallic forces in the metal-metalloid glass are not greatly modified from those in the crystalline form of the metal constituent.     

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.     

Temperature dependence of the electrical resistivity of amorphous Co80−xErxB20 alloys

The temperature dependence of the electrical resistivity of amorphous Co_80−xEr_xB₂₀ alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum T_min. In addition, the resistivity shows quadratic temperature behavior in the interval T_min<T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity shows a change in structural short range occurring in the composition range 8–9 at%.     

Magnetocaloric effect in high-energy ball-milled Gd5Si2Ge2 and Gd5Si2Ge2/Fe nanopowders

Evolution of structure and magnetocaloric properties in ball-milled Gd₅Si₂Ge₂ and Gd₅Si₂Ge₂/0.1 wt% Fe nanostructured powders were investigated. The high-energy ball-milled powders were composed of very fine grains (70–80 nm). Magnetization decreased with milling time due to decrease in the grain size and randomization of the magnetic moments at the surface. The magnetic entropy change (ΔS_M) was calculated from the isothermal magnetization curves and a maximum value of 0.45 J/kg K was obtained for 32 h milled Gd₅Si₂Ge₂ alloy powder for a magnetic field change of 2 T while it was still low in Fe-contained alloy powders. The thermo-magnetic measurements revealed that the milled powders display distribution of magnetic transitions, which is desirable for practical magnetic refrigerant to cover a wide temperature span.     

Thermal and electrical properties of Te80Si20−xPbx glasses

Results of calorimetric, electrical resistivity and X-ray measurements of Te₈₀Si_20?xPb_x glasses are reported. Experimental findings concerning correlations between transformation temperatures obtained from DSC and resistivity measurements are presented. Conduction activation energy is discussed in terms of changes of randomness of amorphous structure caused by concentration changes.     

The electrical resistivity of amorphous alloys at low temperatures

Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu₅₇Zr₄₃, Cu₄₀Zr₆₀ and Pd₃₀Zr₇₀ demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.     

Magnetic after-effects of hydrogen in amorphous Co75Si15B10 alloys

The magnetic after-effect spectrum of hydrogen-charged amorphous Co₇₅Si₁₅B₁₀ and its annealing behaviour was measured in the temperature range between 2.1 and 450 K. A hydrogen related relaxation peak was observed at 190 K with a mean activation energy of 0.42 eV.     

高压下非晶Ti80Si20合金的晶化

非晶Ti₈₀Si₂₀合金在高压下加热时,不发生多相分解,并直接转变为bcc-Ti(Si)过饱和固溶体,这可能与Ti有较大的压缩率及固溶所造成的弹性能比较小等因素有关。 关键词：     

Irradiation effects in amorphous alloy Fe80B20

The Mössbauer effect has been used to study the irradiation effects in the amorphous alloy Fe₈₀B₂₀ after 40 keV helium ion bombardment. Conversion electron Mössbauer spectroscopy reveals the eminent irradiation effects; α-iron phase appears in the damaged region of the sample.     

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.