Efficient single-step Cool-SPS processing of Mn₃O₄ ceramics at 400 C with persistent magnetodielectric coupling

Spinel type Mn3O4 oxide ceramics possess intriguing magnetodielectric properties, but traditional processing routes can be frustrated by limited high temperature phase stability. Using a low temperature (<= 400 degrees C) electric field assisted processing route (Cool-SPS), a highly cohesive Mn3O4 ceramic is achieved. Reactive manganese oxide-hydroxide precursor powder is converted into the targeted Mn3O4 with a single step process under strategically selected conditions. Detailed X-ray diffraction studies, including variable temperature and atmosphere measurements, plus in-situ monitoring of processing parameters, have been combined to map and optimize SPS processing parameters. The microstructure evolution from precursor to ceramic was examined by electron microscopy, while extensive magnetic and dielectric measurements were performed to study the complex physical behavior of Mn3O4 at low temperature (<43 K). The efficacy of this Cool-SPS processing approach for Mn3O4 is demonstrated by the observed ceramic properties, including a hysteretic magnetic-field dependent dielectric response which supports the existence of a magnetoelectric coupling.