I do believe I was mistaken in my original post and that a locally constant magnetic field will not produce an appreciable diamagnetic force. Diamagnetism work

I do believe I was mistaken in my original post and that a locally constant magnetic field will not produce an appreciable diamagnetic force. Diamagnetism works by inducing dipoles in the medium, and a dipole placed in a constant field experiences no net force. It may experience a torque if it is not aligned with the field, but in the case of diamagnetism the induced dipoles are naturally aligned, and so there is neither force nor torque.