Magnetoresistance in an asymmetric Ga_1-xMn_xAs resonant tunneling diode

In a GaMnAs/AlGaAs resonant tunneling diode (RTD) structure, we observe that both the magnitude and polarity of magnetoresistance are bias dependent when tunneling from a three-dimensional GaMnAs layer through a two-dimensional GaMnAs quantum well. This magnetoresistance behavior results from a shift of negative differential resistance features to higher bias as the relative alignment of the GaMnAs layer magnetizations is changed from parallel to antiparallel. Our observations agree with recent predictions from a theoretical analysis of a similar n -type structure by Ertler and Fabian, and our results suggest that further investigation into ferromagnetic RTD structures may result in significantly enhanced magnetoresistance.