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This work describes the production and characterization of a composite material based on magnetite filled HDPE, which is commonly known for its magnetic properties. Composites of this kind are used in different applications such as microwave absorption, transducers and biomedical applications like drug delivery, organs tagging, etc. The samples were produced according to different volume ratios of magnetite and HDPE. The semiquantitative analysis conducted by XRD revealed the presence of hematite within the mineral magnetite used as a filler in the composites. The crystallinity degree was calculated through X-ray diffraction tests. The XRD results showed how there is an amorphous-crystalline transition due to the magnetite increasing content. The crystallinity percent (χ c ) for samples filled with 40% of magnetite volume was 90% while the (χ c ) for samples filled with 10% of magnetite volume was 80%. Which may be related to the increased magnetite particles into the plastic matrix for reinforcement contents up to 30% by volume, as evidenced in the images obtained through scanning electron microscopy (SEM). The samples were electrically characterized through volume resistivity measurements and electric polarization. The results showed that for ratios less than the 20% of magnetite there is no substantial reduction in the resistivity of the composite samples compared to the unfilled HDPE samples, but for magnetite ratios above 30% the composite samples showed a substantial reduction of six orders of magnitude in their volumetric resistivity. The electric polarization showed how the composite material undergoes a transition, going from an insulating material (for samples with 10% of magnetite volume) to a resistive material where the current and voltage are in phase (for samples with 30% and 40% of magnetite volume). The magnetization curves showed that the saturation magnetization (from 17,3 to 60,5 emu/g) and remanence (from 0,94 to 5 emu/g) increase in samples with high magnetite contents. The presence of the hematite phase in the samples could have affected the magnetization saturation and the remanence values in the hysteresis curves. Magnetization curves as a function of temperature showed the Verwey samples transition around the 120K and confirmed that the magnetization increases as the magnetite volume within the matrix increases. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat. Key words: High density polyethylene; Magnetite; Plastic composites, Structural properties electric properties; Magnetic properties.Producción y caracterización estructural, eléctrica y magnética de un material compuesto a base de magnetita pulverizada y polietileno de alta densidad. ResumenSe describe la producción y caracterización de un material compuesto basado en matrices de polietileno de alta densidad (HDPE) reforzadas con magnetita pulverizada. Compuestos de este tipo son usados para diferentes aplicaciones como la fabricación de escudos de absorción electromagnética, transductores, entrega focalizada de medicamentos, ma...

In this work we report the synthesis of RuSr 2 GdCu 2 O 8/ La 0.67 Sr 0.33 MnO 3 superconducting-magnetic composites with 50 vol.% of both RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds. Structural characterization was performed by X-ray diffraction, which permitted us to establish the absence of other crystallographic phases and the non-reactive character of the compounds into the composite. Scanning electron microscopy showed the sub-micrometric size of the grains. Energy dispersive X-ray experiments confirmed chemical stability between RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds in the composites. Resistivity measurements provided evidence of superconducting transition for the RuSr 2 GdCu 2 O 8 material, with TSC=39.2 K. Results of magnetization as a function of temperature corroborated the superconducting transition and showed the expected antiferromagnetic character of the Ru perovskite, with a Néel temperature TN=132.7 K. Systematic measurements of applied magnetic field up to 5 kOe were performed at these temperature regimes: TN < T < TC (with TC being the Curie temperature of the La 0.67 Sr 0.33 MnO 3 compound); TSC < T < TN; and T < TSC. Our results reveal the ferromagnetic character of the composites at the temperature regime TN < T < TC. The exchange bias effect was observed for weak applied fields (H < 1.5 kOe) at temperatures between TSC < T < TN. At the superconducting regime (T < TSC) weaker exchange bias is observed for low magnetic fields (H < 1 kOe). For strong magnetic fields (H > 2 kOe) the ferromagnetic character of the system is recovered.

We report structural, morphological and magnetic properties of the Sr 2 GdRuO 6 compound, which is used as precursor oxide in the production process of RuSr 2 GdCu 2 O 8 superconducting ruthenocuprates. The crystalline structure was studied by X-ray diffraction and Rietveld refinement. Results reveal that material crystallizes in a monoclinic double perovskite, space group P2 1 /n (#14). Scanning Electron Microscopy experiments on samples show homogeneous granular morphology with grain size from 3 up to 7 μm. Semiquantitative analysis of composition was performed by the Energy Dispersive X-ray technique. Experimental results are 98% in agreement with the theoretical stoichiometry. Curves of magnetization as a function of temperature exhibit an antiferromagnetic-like behaviour, with Néel temperature T N =15.3 K and magnetic effective moment 8.72 μ B .