Crystallographic and magnetic investigation on W-type-hexaferrite single crystals in the solid solution series SrZn2-xCoxFe16O27

The saturation magnetization and the magnetocrystalline anisotropy were measured on single crystals in the solid solution series SrZn
2-x
Co
x
Fe
16
O
27
(SrZn
2-x
Co
x
-W) at 298 K and 6 K. Lattice constants and Curie-temperatures are also given as a function of the composition. The magnetocrystalline anisotropy changes from uniaxial to planar dependent on temperature and cobalt substitution at
x \approx 0.5
for 6 K and
x \approx 0.85
for 298 K. The six-fold anisotropy in the basal plane of the planar W-hexaferrites increases strongly with increasing cobalt content. Crystals with a low Co substitution (x = 0.33 and 0.67) have an anomalous discontinuity in their hard direction magnetization curves; indicating a first-order magnetization process.