Quantum theory of tunneling magnetoresistance in GaMnAs/GaAs/GaMnAs heterostructures

Using a quantum theory including spin-splitting effect in diluted magnetic semiconductors, we study the dependence of tunneling magnetoresistance (TMR) on barrier thickness, temperature and applied voltage in GaMnAs/GaAs/GaMnAs heterostructures. TMR ratios more than 65% are obtained at zero temperature, when one GaAs monolayer (≈0.565nm) is used as a tunnel barrier. It is also shown that the TMR ratio decreases rapidly with increasing barrier thickness and applied voltage; however, at high voltages and low thicknesses, the TMR first increases and then decreases. Our model calculations well explain the main features of the recent experimental observations.