Electron Tunneling into Films of Ni, Pd, and NiPd Alloys

Abstract

Film tunnel junctions Al–I–M (M is an evaporated film of Ni, Pd, a series of NiPd alloys, Fe, and Gd) have been investigated by measuring the I‐V characteristic and G(dI/dV) vs V over the range 0–2 V. The aim of the investigation was to see if excitation of spin waves by the tunneling electron is observable in the tunneling characteristic. The result to data is that the rather complex results cannot be interpreted using such simple arguments. At voltages >500 mV the G vs V plot is noticeably asymmetrical about V=0 for Ni and the alloys, the conductance being smaller for the bias corresponding to electrons tunneling into nickel. This may be a weak reflection of the low density of d‐band states well above the Fermi level compared to the high density near and below the Fermi level. At low voltages in Ni a peak in conductance is observed which is asymmetrical about V=0; its width scales approximately with the Curie temperature in the NiPd alloys. Drastic changes at both high and low voltages were obtained when Ni was evaporated in an applied magnetic field. Interesting but very small features, which are observed in G vs V for Al–I–Pd junctions, are presented.