Substantially harder, actually. The NMR frequency is directly proportional to the strength of the magnetic field. Unless you're going to put the objects in question _into_ the magnet, you won't have it at that field, so an NMR frequency is irrelevant.
Additionally - NMR resonates the _nucleus_. Absent a rather substantial RF pulse, the interactions with the electrons (and therefore anything chemical) are nearly zero. NRM needs the static field, _and_ a gradient pulse in each of 3 axis, _and_ and RF pulse, to measure anything.
Generating an EMP is orders of magnitude more simple.
Dave Hinz (worked in engineering on MRI scanners for a dozen years)