| NMR provides a spectroscopic probe of magnetic order and of its excitations. Basic magnetic properties may be investigated by magnetometry. Magnetic structures and excitations of homogeneous materials are provided by neutrons and sometimes X-rays. When dealing with subtler aspects of complex magnetic materials (such as oxide spinels and perovskites, pyrochlores, pnictides) each nucleus additionally offers a different local view.
Nuclei of magnetic elements experience very large magnetic fields (tens of Tesla per Bohr magneton). Other non magnetic elements probe smaller transferred hyperfine and dipolar fields. This site-specific answer is extremely helpful when diffraction and macroscopic techniques do not provide a complete picture.