Tunneling Magnetoresistance Properties in Ballistic Spin Field-Effect Transistors

We investigate tunneling magnetoresistance (TMR) properties in ballistic spin field-effect transistors (SFETs) by taking into account the Rashba spin-orbit coupling (SOC), interface scattering, the presence of an in-plane magnetic field, band mismatch, and spin polarization in the ferromagnetic electrodes. It is shown that, for high potential barriers at the contact/channel interfaces, as the band mismatch is varied, the magnitude, amplitude, phase, and sign of the TMR are significantly modulated by the Rashba SOC, whereas the presence of the magnetic field makes the TMR oscillate between positive and negative values. Likewise, in an SFET with ohmic-contact interfaces, the Rashba SOC affects the band mismatch dependence of the TMR in a completely different fashion from the magnetic field. We also study the variation in the TMR when either the Rashba SOC strength or the magnitude or direction of the magnetic field is varied. Our theoretical results may be useful in analyzing experimental data of relevant devices.