Transport properties and point contact spectra of Ni_xNb_{1-x} metallic glasses

Halbritter, A.; Kolesnychenko, O. Yu.; Mihaly, G.; Shklyarevskii, O. I.; van Kempen, H.

Transport properties and point contact spectra of Ni_xNb_{1-x} metallic glasses

Authors

Halbritter, A.

Kolesnychenko, O. Yu.

Mihaly, G.

Shklyarevskii, O. I.

van Kempen, H.

Description

Bulk resistivity and point contact spectra of Ni_xNb_{1-x} metallic glasses have been investigated as functions of temperature (0.3-300K) and magnetic field (0-12T). Metallic glasses in this family undergo a superconducting phase transition determined by the Nb concentration. When superconductivity was suppressed by a strong magnetic field, both the bulk sample R(T) and the point contact differential resistance curves of Ni_xNb_{1-x} showed logarithmic behavior at low energies, which is explained by a strong electron - "two level system" coupling. We studied the temperature, magnetic field and contact resistance dependence of Ni_{44}Nb_{56} point-contact spectra in the superconducting state and found telegraph-like fluctuations superimposed on superconducting characteristics. These R(V) characteristics are extremely sensitive detectors for slow relaxing "two level system" motion.
4 pages, 5 figures