magnetic cages (like the one picture below) allow us to generate magnetic fields in any direction in 3D, with strengths ranging from 0 Gauss up to 3 x earth's field.
Each of the three coil systems is composed of four squares (four square Merritt coil design). Each system creates a magnetic field in either the X, Y, or Z direction. For each system two separate wire systems that can be run in parallel (to create a single magnetic field in the desired direction), or in antiparallel (to pass the same amount of current through the system without generating a magnetic field). High resolution 1/100°C permanently installed in the center and periphery of the cage constantly report any slight temperature fluctuation (a fan constantly blows air on the system to prevent any thermal gradient from developing).
The AFD neurons (above) are necessary and sufficient for animals orienting to magnetic fields. We showed that these cells respond to magnetic stimuli.