Problems of nuclear magnetism in magnetically ordered substances

Results of studies into the properties of magnetically ordered substances that have been obtained by nuclear magnetic resonance (NMR) methods for the last ten years are reviewed. Materials of three types are discussed. These are, first, precipitation-hardening alloys Fe-Co-Cr, which are used as materials for the production of permanent magnets; second, quasi-one-dimensional antiferromagnets, which are of interest in association with a fundamental problem of the physics of magnetism such as the problem of magnetic sublattices; and third, the antiferromagnetic compound KMnF3, for which a giant magneto-acoustic effect was discovered. The later effect is comparable in magnitude to the electronic magnetoelastic effects, although it is due to nuclear magnetism, which is 10(5) times weaker than the electronic interactions.