[sam2010 (OP)]

I own a safety company in which we use coded magnets to provide safety on machines.  It is a two part system consisting of actuator (magnet) and read head (reed contacts).  When the magnet comes within the readable range, it closes the reed contacts and starts the machine.  I need a thin piece of metal that I can put between the actuator and read head to block the magnetic field.  Steel works but the steel plate is attracted to the magnet and causes door problems.  Is there a nonmagnetic material that will block the magnetic field?  Thank you in advance for your comments and suggestions.