Bovda V. Structure and magnetic properties of amorphous-crystalline alloys on the base of Nd-Fe-B system.

Thesis presents study of structural and magnetic properties of exchange-coupled magnetic alloys on the base of Nd-Fe-B system. The influence of heat treatment conditions and Nd concentration of melt-spun alloys and bonded magnets were investigated and discussed. A detailed investigation into the effects of pulsed plasma streams on magnetic alloys is made. The conditions of formation of an amorphous structure without crystalline phases in the PVD films are established. For the first time, the polyhedral structure of Nd2Fe14B and Nd2Fe23B3 phases described on the basis of the definition of coordination as the first largest interval in the sequence of distances from the atoms of a given atom (gap method). It is shown the existence of polyhedra which are not subjected to the restrictions for simple Frank-Kasper tetrad structures. The results are the physical basis for the optimization of nanocrystalline magnetic alloys and their practical application in industry. Keywords: melt-spinning, magnetic nanocomposites, coercitivity, remanence, exchange-coupled magnets, pulsed plasma treatment, metastable phases, coordinational polyhedron.