Two new series of W-type hexagonal ferrites containing monovalent copper

Abstract

Improvement of the Zn 2-W type hexagonal ferrite as hard magnetic material for permanent magnet applications is obtained by using the partial substitution of Zn 2+ by a suitable combination of monovalent and trivalent cations. The magnetic specification (the magnetization σ s, the anisotropy field H a, the first magnetic anistropy constant K 1, the Curie temperature T c) of these new W-type phases are better than the previously known Zn 2-W or Fe 2-W ones. Furthermore, the calcining time required to get a pure W phase containing lithium or monovalent copper is considerably reduced as compared to the time required to obtain pure Zn 2-W or Fe 2-W phases. Magnetic behaviors are studied as a fonction of different annealing temperatures; below 1030°C, the decreasing of the magnetization is interpreted as the consequence of the copper oxidation phenomenon.