The microstructure and magnetic properties of Nd8.5Tb1.5Fe83Zr1B6 ribbons obtained at various cooling rates

Modern Re-Fe-B hard magnetic materials, produced using rapid quenching technique, taking into account variations in chemical composition, can be divided into three groups i.e. of stoichiometric, Re2Fe14B composition, and with excess of rare earth or iron [1–3]. Materials, composed of Re-Fe-B compound with overstoichiometric rare earths, typically are characterized by worse glass transition ability, smallest Mr/Ms ratio and large coercivity. Their properties are shaped by exchange interactions between Re2Fe14B, which are weakened by an increased distance between the grains. Enlarged distance between grains is resulting from the presence of a thin boundary formed from an amorphous matrix of redundant rare earths. Additionally, the presence of such a boundary causes an increase in coercivity due to the strong bonding of domain walls at the grain boundaries [4]. The stoichiometric composition causes increase in glass transition ability, Mr/Ms ratio but also causes deterioration of coercivity. These changes are a result of a reduction in the distance between grains, by removing the paramagnetic amorphous matrix, and fi ner structure as a result of increase in glass transition ability [5]. The highest glass transition ability, fi ner structure and highest Mr/Ms ratio is met in Re-Fe-B compound with overstoichiometric iron. The signifi cantly higher value of the Mr/Ms ratio results from the presence of the strong exchange interactions, between particles that differ in magnetic hardness. The grains, of soft magnetic phase, have The microstructure and magnetic properties of Nd8.5Tb1.5Fe83Zr1B6 ribbons obtained at various cooling rates Marcin Dośpial, Jacek Olszewski, Marcin Nabialek, Pawel Pietrusiewicz, Tomasz Kaczmarzyk