It has been shown in an earlier publication [J. Pendlebury et al. Phys. Rev. A 70, 032102 (2004)] that magnetic-field gradients applied to particles in traps can induce Larmor frequency shifts that may falsely be interpreted as electric-dipole moment 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 $⟨\partial B_z∕\partial z⟩$.

• Received 18 October 2005

DOI:https://doi.org/10.1103/PhysRevA.73.014101