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Ferromagnetism at room temperature in perovskites CaCu<inf>3</inf>Ti<inf>4</inf>O<inf>12</inf> mixes with ZnO and TiO<inf>2</inf>

Abstract:

In this work we report ferromagnetism at room temperature and electrical transport effects above room temperature in CaCu3Ti4O12+ (ZnO or TiO2) mixtures. From the Electron Paramagnetic Resonance (EPR) we derived the spectrum of the resonance field (HR) and line width peak to peak (HPP). The magnetization of the samples was studied as a function of the temperature. Weak ferromagnetism was found in four blends made by the mechanical milling method. This fact is attributed to a double magnetic exchange enabled by a possible effect of a partial diffusion at the grain interfaces between the CaCu3Ti4O12 and the oxides (ZnO or TiO2). This possible partial diffusion, due to a closed contact between the particles, is observed in the mixtures by using scanning electron microscopy. We correlate the behavior of the peak to peak line width with the electrical conduction around 400K.