A new series of materials for permanent magnets: The W ferrites BaZn 2(1− x) (LiFe) xFe 16O 27

Abstract

The possibility of improving the W-type hexagonal ferrite BaZn 2-W in order to use it as a hard material for permanent magnets will be demonstrated through the partial substitution of Zn 2+ cations according to the scheme 2 Zn 2+ ↔ Li + + Fe 3+ Such a partial substitution leads to a new series of compounds with W-type structure whose magnetic specifications are just as good as those of the previously known Zn 2-W or Fe 2-W ferrites. Furthermore, synthesis conditions are less stringent to atmosphere or calcining times. The new phases obtained by a combination of monovalent, bivalent and trivalent cations lead to products suitable to be used as permanent magnet materials (80 uem/g at room temperature with H a = 12 kOe and T C=430°C or 75 uem/g at RT with H a=11.5 kOe and T C=518°C). We propose a model for the distribution of the lithium through the different sublattices which leads to a good agreement between the observed magnetization at 4.2 K and the value we calculated using collinear Gorter's model.