Dipole-Field Contributions to Geometric-Phase-Induced False   Electric-Dipole Moment Signals for Particles in Traps
  It has been shown in an earlier publication that magnetic field gradients applied to particles in traps can induce Larmor frequency shifts that may falsely be interpreted as electric-dipole moment (EDM) signals. This study has now been extended to include nonuniform magnetic field gradients due to the presence of a local magnetic dipole. It is found that, in the high orbit-frequency regime, the magnitude of the shifts can be enhanced beyond the simple expectation of proportionality to the volume-averaged magnetic-field gradient. 
P. G. Harris and J. M. Pendlebury