Spin fluctuations in metallic glasses Zr75(NixFe1-x)25 at ambient and higher pressures

Positive and Negative Temperature Dependence in the Resistivity of Crystallized Zr-Fe-Ni Metallic Glasses

Ni_0.25Fe_0.75Zr₃ metallic glassy ribbons were annealed in evacuated quartz ampoules beyond the crystallization temperatures (T_x ~655 K) over the range 773 to 1,173 K for varying periods of time. The resistivity of samples annealed over the temperature range 923 to 1,073 K for periods less than four hours increased as a function of decreasing temperature, while it decreased for samples annealed for more than four hours or at temperatures below 923 K or above 1,073 K for any period of time. All the annealed samples were found to contain only Ni, Fe and Zr from energy dispersive X-ray (EDX) analyses.

Electron-phonon coupling and spin fluctuations in 3d and 4d transition metals: implications for superconductivity and its pressure dependence

We have calculated the electron-phonon coupling for the complete 4d series and the nonmagnetic 3d transition metals using the linear response method and the linear muffin-tin orbitals' basis. A comparison of the linear response results and those obtained via the rigid muffin-tin approximation is provided. Based on the calculated values of the electron-phonon coupling constants, band density of states and the measured values of the electronic specific heat constants, we estimate the spin-fluctuation effects, i.e. the electron-spin-fluctuation (electron-paramagnon) coupling constants in these systems. For the sake of comparison, several other metals, Cu, Zn, Ag, Cd, Al and Pb, are also studied. Alternative estimates of the electron-paramagnon coupling constants are obtained from the values of the Stoner parameters and the band densities of states at the Fermi level. Implications of these results on the superconductivity and its pressure dependence as well as the alloying effects of superconductivity in these systems are discussed. It is pointed out that spin fluctuations play an important role in the validity of the Matthias rule that in metallic systems the optimum conditions for (electron-phonon) superconductivity occur for 5 and 7 valence electrons/atom.