The invention provides a nanocomposite magnet, which has achieved high coercive force and high residual magnetization. The magnet is a non-ferromagnetic phase that is intercalated between a hard magnetic phase with a rare-earth magnet composition and a soft magnetic phase, wherein the non-ferromagnetic phase reacts with neither the hard nor soft magnetic phase. A hard magnetic phase contains Nd.sub.2Fe.sub.14B, a soft magnetic phase contains Fe or Fe.sub.2Co, and a non-ferromagnetic phase contains Ta. The thickness of the non-ferromagnetic phase containing Ta is 5 nm or less, and the thickness of the soft magnetic phase containing Fe or Fe.sub.2Co is 20 nm or less. Nd, or Pr, or an alloy of Nd and any one of Cu, Ag, Al, Ga, and Pr, or an alloy of Pr and any one of Cu, Ag, Al, and Ga is diffused into a grain boundary phase of the hard magnetic phase of Nd.sub.2Fe.sub.14B.

The critical current density of a superconducting bulk of an iron-based compound is improved compared with those of conventional superconducting bulks. A superconducting bulk (B) is a polycrystal of an iron-based superconductor, and has a degree of c-axis orientation, as determined by Lotgering's method, of not less than 0.2.

Reagent complexes have two or more elements, formally in oxidation state zero, complexed with a hydride molecule. Complexation with the hydride molecule may be evidenced by shifts to lower binding energies, of one or more electrons in each of the two or more elements, as observed by x-ray photoelectron spectroscopy. The reagents can be useful for the synthesis of multi-element nanoparticles. Preparation of the reagents can be achieved by ball-milling a mixture that includes powders of two or more elements and a hydride molecule.

A novel class of reagents, useful for synthesis of elemental nanoparticles, includes at least one element, formally in oxidation state zero in complex with a hydride molecule. The reagents can optionally include an additional ligand incorporated into the complex. Elemental nanoparticles are synthesized by adding solvent to the reagent, optionally with a free ligand and/or a monoatomic cation.

A rare earth sintered magnet is an anisotropic sintered body comprising Nd.sub.2Fe.sub.14 B crystal phase as primary phase and having the composition R.sup.1.sub.aT.sub.bM.sub.cSi.sub.dB.sub.e wherein R.sup.1 is a rare earth element inclusive of Sc and Y, T is Fe and/or Co, M is Al, Cu, Zn, In, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, or W, a to e are 12a17, 0c10, 0.3d7, 5e10, and the balance of b, wherein Dy and/or Tb is diffused into the sintered body from its surface.