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

Abstract

The superconducting properties of metallic glasses Zr{sub 75}(Ni{sub {ital x}}Fe{sub 1{minus}{ital x}}){sub 25} ({ital 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}{sub SF} the following measurements were carried out: the dc magnetic susceptibility, the upper critical field at the ambient pressure superconducting transition temperature {ital T}{sub {ital c}} ({ital P}=1 bar), mass density, and room temperature resistivity. From the pressure dependence of the superconducting transition temperature {ital T}{sub {ital c}}({ital P}) in Cu{sub 25}Zr{sub 75} glass, we estimate the volume derivative of the electron-phonon ({ital e}-ph) coupling parameter {lambda}{sub {ital e}-ph} in this alloy using the McMillan equation. This is used as a reference value for the volume derivative of {lambda}{sub {ital e}-ph} in the Zr{sub 75} (Ni{sub {ital x}}Fe{sub 1{minus}{ital x}}){sub 25} alloys. Using the modified McMillan equation, which includes spin fluctuation effects and the above reference value for the volume derivative of the {ital e}-ph coupling parameter, we determine {lambda}{sub {ital e}-ph}, the electron-spin fluctuation coupling parameter {lambda}{sub SF}, and the rate of suppression of spin fluctuations with the pressure ({ital d} ln{lambda}{sub SF}/{ital d} ln{ital V}) as a functionmore » of Fe concentration in these alloys. Both spin fluctuations and the rate of suppression of spin fluctuations with pressure ({ital d} ln{lambda}{sub SF}/{ital d} ln{ital V}) are found to increase with higher Fe concentration in these alloys.« less