An NMR scanner apparatus uses a permanent magnet comprised of an assembly of magnetic material formed of a substantial number of low energy permanent magnetic elements producing magnetic flux and arranged in at least one row of columns. A frame of magnetically soft material provides a return path for...http://www.google.co.uk/patents/US4707663?utm_source=gb-gplus-sharePatent US4707663 - Nuclear magnetic resonance apparatus using low energy magnetic elements
