Spin fluctuations in metallic glasses ${\mathrm{Zr}}_{75}$(${\mathrm{Ni}}_{\mathit{x}}$${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$${)}_{25}$ at ambient and higher pressures

The superconducting properties of metallic glasses ${\mathrm{Zr}}_{75}$(${\mathrm{Ni}}_{\mathit{x}}$${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$${)}_{25}$ (x=0,0.25,0.50,0.75,1.0) were studied both at ambient pressure and under quasihydrostatic pressure up to 8 GPa (80 kbar). To obtain information on the spin fluctuation parameter ${\lambda }_{\mathrm{SF}}$ the following measurements were carried out: the dc magnetic susceptibility, the upper critical field at the ambient pressure superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ (P=1 bar), mass density, and room temperature resistivity. From the pressure dependence of the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$(P) in ${\mathrm{Cu}}_{25}$${\mathrm{Zr}}_{75}$ glass, we estimate the volume derivative of the electron-phonon (e-ph) coupling parameter ${\lambda }_{\mathit{e}\mathrm{-}\mathrm{ph}}$ in this alloy using the McMillan equation. This is used as a reference value for the volume derivative of ${\lambda }_{\mathit{e}\mathrm{-}\mathrm{ph}}$ in the ${\mathrm{Zr}}_{75}$ (${\mathrm{Ni}}_{\mathit{x}}$${\mathrm{Fe}}_{1\mathrm{-}\mathit{x}}$${)}_{25}$ alloys. Using the modified McMillan equation, which includes spin fluctuation effects and the above reference value for the volume derivative of the e-ph coupling parameter, we determine ${\lambda }_{\mathit{e}\mathrm{-}\mathrm{ph}}$, the electron-spin fluctuation coupling parameter ${\lambda }_{\mathrm{SF}}$, and the rate of suppression of spin fluctuations with the pressure (d ln${\lambda }_{\mathrm{SF}}$/d lnV) as a function of Fe concentration in these alloys. Both spin fluctuations and the rate of suppression of spin fluctuations with pressure (d ln${\lambda }_{\mathrm{SF}}$/d lnV) are found to increase with higher Fe concentration in these alloys.