请问永磁体核磁与超导核磁相比有何优势和不足？

The upper
limit for the magnetic field strength that can be achieved
by iron magnet technology is about 2.35 T. The
discovery of superconducting materials which lose all
their resistance when cooled below a certain temperature
made it possible to manufacture higher field magnets
resulting in increased dispersion and sensitivity.

由于人造永久磁体的生产 (钢加某些稀土元素配方), 目前永久磁体的磁力, 已经可以用来生产 300 兆 NMR 谱仪.
这样的谱仪, 免除了液氮与液氦的费用.