Texture formation in W-type hexaferrite by cold compaction of non-magnetic interacting anisotropic shaped precursor crystallites

Crystallites of the W-type hexaferrites, Sr(Ni1-xZnx)2Fe16O27 (x = 0, 0.5, 1) have been aligned without applying magnetic field nor hot compaction, but through a simple synthesis process taking advantage of easy alignment of non-magnetic interacting, anisotropic-shaped precursor crystallites of goethite. The goethite precursor was prepared through a simple hydrothermal synthesis route, forming lathlike crystallites with apparent dimensions of 23.3 × 40.1 × 11.0 nm3 as extracted from powder X-ray diffraction along the a-, b- and c-axis, respectively. The calcined pellets consisted of almost phase pure W-type hexaferrites with relative small impurities of spinel ferrite (≤9.02(3) wt%). The high synthesis temperature resulted in large crystallites, which in turn caused low coercivities (Hc ≤ 5.4(1) kA m-1) and a squareness ration (Mr/Ms, remanence (Mr) over saturation magnetisation (Ms)) close to zero for all samples. The vanishing coercivity makes Mr/Ms an unsatisfying measure of preferred orientation. Quantitative texture analysis of the samples was carried out based on 2D transmission synchrotron diffraction data collected at different orientations of the samples. The texture investigations revealed alignment of the crystallites with the c-axis normal to the pressing surface of the pellets. The SrNi2Fe16O27 sample showed the highest texture index of 7.5 m.r.d.2.