Conducting ballistic magnetoresistance and tunneling magnetoresistance:: Pinholes and tunnel barriers

This letter shows that conducting ballistic and tunneling magnetoresistances have identical physical treatments and, therefore, it is not possible to distinguish whether an experiment is measuring, in oxide barriers, electron conduction through pinholes or tunneling because both types of conduction are governed by the same physics. Currents in both cases are calculated by matching wave functions at the electrodes (both are ballistic). Therefore, pinholes or small ballistic nanocontacts in the tunnel barrier allow conducting ballistic electrons that account for most of the current. We also show that, in the case of nonsuperconducting materials, e.g., magnetic materials, current-voltage characteristics are not suitable to distinguish one process from the other. (C) 2000 American Institute of Physics. [S0003-6951(00)04835-X].