Magnetic resonant tunneling devices (RTDs) have been recognized as one possible route to developing a near ideal spin valve. With the advent of dilute magnetic semiconductors, the ability to grow these devices using traditional semiconductor techniques provides a distinct advantage over present metal-based giant magnetoresistance devices. We examine the effect of replacing dilute magnetic semiconductor leads (GaMnAs) with Ga0.5Mn0.5As monolayers adjacent to the RTD structure. We examine transmission through a series of GaAs/AlAs RTDs using principal layer Green function technique in the linear muffin-tin orbital framework. Self-consistent calculations using a linear response technique are done for both nonmagnetic RTDs and ones with Mn doped layers outside the AlAs barriers. The Mn dopant layers lead to splitting of the transmission peaks in both the conduction and the valence bands. The transmission peaks shift as the quantum well width increases in accordance with quantum well states. In addition, transmission in the minority spin channel is suppressed as valence quantum well states move closer to the Fermi energy. Preliminary zero bias conductance calculations give tunneling magnetoresistance values in excess of 1000%. While this estimate does not include spin scattering sources such as spin-orbit coupling, the actual tunneling magnetoresistance should still be very high. © 2003 American Institute of Physics.