Coercivity and interactions in coprecipitated and ceramic SrFe12O19 (Sr‐M) hexaferrite samples were studied using remanence curves and magnetic viscosity in addition to microstructural considerations by means of SEM analysis. Following a magnetic viscosity formalism, the activation volume was obtained and interactions were evaluated using the ΔM technique. Even for a coprecipitated sample with a high coercive field (Hc = 6100 Oe), the experimental activation volume indicates a non‐coherent mechanism for magnetization reversal and demagnetizing‐like interactions were found in this isotropic sample with large aspect ratio particles; also demagnetizing‐like interactions were found for a thermally treated coprecipitated sample and a ceramic sample.
In this work, the so‐called global model for magnetization reversal is applied to describe the coercive field temperature dependence in fine barium and strontium M‐hexaferrites (75–300 K range). Using magnetic viscosity measurements, the temperature dependence of the activation volume for magnetization reversal was obtained. In this temperature range, the coercive field (as the anisotropy field) increases with increasing temperature. However, it is found experimentally that the activation volume also increases with temperature and then the physical interpretation of the model is partially not clear.
Conventional solid state reaction method, from oxides and carbonates, was employed to prepare bismuth (Bi)-based multiferroic systems. The undoped BiFeO3 (BFO) and the codoped system with Ba, La and Ti (Bi[Formula: see text]BaxFe[Formula: see text]TiyO3, Bi[Formula: see text]BaxLazFe[Formula: see text]TiyO3) with x,y,[Formula: see text] were prepared stoichiometrically and sintered at two different temperatures. The structural and magnetic properties were investigated at room temperature. XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system. For the undoped system, some reflections of undesired phases are present for two different sintering temperatures, while for the doped system only one phase is present for both temperatures. The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples. The results show that for undoped BFO system, spontaneous magnetization is not observed at room temperature. Nevertheless, in doped one, a well-defined ferromagnetic behavior is observed at room temperature, possible, due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi–O bonds. The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe[Formula: see text] and Fe[Formula: see text] in all the studied samples. Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Néel temperature but possibly yes in ferroelectric-paraelectric transition.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.