Surfactant-Assisted Hydrothermal Synthesis and Magnetic Properties of Urchin-like MnWO₄ Microspheres

Three-dimensional (3D) urchin-like MnWO 4 microspheres with a diameter of ca. 1−1.2 μm assembled by nanorods with a length of 240 nm and an aspect ratio of ca. 9 have been fabricated by a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) assisted hydrothermal method. The result demonstrated that CTAB played an important role as a soft template in directing growth and self-assembly of urchin-like MnWO 4 microspheres, and suitable pH values and reaction temperature are also essential for the formation of urchin-like microspheres. Magnetic measurement indicates that urchin-like MnWO 4 microspheres show a weak ferromagnetic ordering at low temperature due to spin-canting and surface spins of microspheres, while much shorter MnWO 4 nanorods show antiferromagnetism at low temperature.