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W-type barium hexaferrite platelets Ba(ZnxCo1−x)2Fe16O27 (0.1 ≤ x ≤ 0.9) were prepared by a chemical coprecipitation route. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 0.5 to 1.5 μm. With increasing x, the coercivity decreased, whereas the saturation magnetization increased. Microwave absorption properties were investigated in the frequency range of 8–12 GHz. An optimal reflection loss (−24.8 dB) reached at 10 GHz for x = 0.5 with a thickness of 2 mm. These results indicated that our samples might be a potential candidate for permanent magnets and microwave absorption materials.

For polycrystalline FeCr2S4, temperature dependence of low-field magnetization shows a step-like transition around orbital ordering temperature Too ∼ 9 K. In this paper, the origin of the magnetic anomaly has been studied. We show that, with increasing magnetic field, the step-like anomaly in M–T curve is gradually suppressed. However, the external magnetic field up to 5 T has no evident influence on orbital ordering transition as revealed by specific heat measurements. Too was increased when an ultrahigh magnetic field, e.g., 14 T, has been applied. Being contrary to the inert response to magnetic field, the Too is sensitive to the variation of external pressure. M(H) curves measured at different temperatures suggest that magnetic anisotropy changes oppositely going across Too. By considering the variation of magnetocrystalline symmetry induced by orbital ordering, the magnetic anomaly around Too has been explained.