  Double-tearing modes (DTMs) have been proposed as a driver of `off-axis
sawtooth' crashes in reverse magnetic shear tokamak configurations. Recently
differential rotation provided by equilibrium sheared flows has been shown
capable of decoupling the two DTM resonant layers, slowing the growth the
instability. In this work we instead supply this differential rotation using an
electron diamagnetic drift, which emerges in the presence of an equilibrium
pressure gradient and finite Larmor radius physics. Diamagnetic drifts have the
additional benefit of stabilizing reconnection local to the two tearing layers.
Conducting linear and nonlinear simulations with the extended MHD code MRC-3d,
we consider an m=2, n=1 cylindrical double-tearing mode. We show that
asymmetries between the resonant layers and the emergence of an ideal MHD
instability cause the DTM evolution to be highly dependent on the location of
the pressure gradient. By locating a strong drift near the outer, dominant
resonant surface are we able to saturate the mode and preserve the annular
current ring, suggesting that the appearance of DTM activity in advanced
tokamaks depends strongly on the details of the plasma pressure profile.
