Surfactant-assisted hydrothermal synthesis and magnetic properties of urchin-like MnWO4 microspheres

Three-dimensional (3D) urchin-like MnWO4 microspheres with a diameter of ca. 1-1.2 mu m 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 MnWO4 microspheres, and Suitable pH values and reaction temperature are also essential for the formation of urchin-like microspheres. Magnetic measurement indicates that Urchin-like MnWO4 microspheres show a weak ferromagnetic ordering at low temperature due to spin-canting and Surface spins of microspheres, while much shorter MnWO4 nanorods show antiferromagnetism at low temperature.