A magnetic core flux canceling device according to embodiments of the present invention includes a magnetic field sensor adapted for placement at a ferrite material core in an implantable medical device, the magnetic field sensor adapted to transmit a signal corresponding to a magnitude of a first magnetic field. Such a device may also include a coil disposed around the ferrite material core and a driver circuit configured to receive the signal and to vary a voltage applied across the coil based on the signal, the voltage applied across the coil creating a second magnetic field at least partially in a direction opposite the first magnetic field. According to some embodiments of the present invention, multiple coils may be used to cancel magnetic fields in multiple directions. A voltage applied across the coil varies in magnitude and/or direction to cancel or weaken an MRI-related magnetic field.
