Magnetic unipolar features in con- ductivity of point contacts between normal and ferromagnetic d-metals (Co, Ni, Fe)

TL;DR

This paper reports on magnetic unipolar features observed in the conductivity of point contacts between normal and ferromagnetic metals, linked to magnetization excitations induced by high current densities, with effects confirmed by magnetic field application.

Contribution

It demonstrates that current-induced magneto-conductance effects are more general than previously thought, occurring in non-ballistic regimes and driven by elastic electron scattering at N--F interfaces.

Findings

Abrupt 1% changes in differential resistance at high current densities.

Features shift with external magnetic field, confirming magnetic origin.

Effects observed in non-ballistic, elastic scattering regimes.

Abstract

In nanocontacts between normal and ferromagnetic metals (N--F) abrupt changes of the order of 1% are detected in differential resistance, dV/dI(V), versus bias voltage, V, on achieving of high current densities, ~10^9 A/cm^2. These features in dV/dI(V) are observed when the electron flow is directed from the nonmagnetic metal into the ferromagnet and connected with magnetization excitations in the ferromagnet induced by the current. Applying an external magnetic field leads to a shift of the observed features to higher biasing current, confirming the magnetic nature of the effect. Such effects are observed for the non-ballistic (not spectral) regime of current flow in the nanocontacts. Thus, the current induced magneto-conductance effects in multilayered N--F structures (nanopillars) extensively studied in the recent literature have much more general character and can be stimulated by elastic electron scattering at single N--F interfaces.