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Effect of cationic order and origin of the dielectric anomalies in La2MnCoO6

AuthorsFrontera, Carlos CSIC ORCID; Barón-González, A. J.; García Muñoz, Josep Lluís; Rivas-Murias, B.; Blasco, Javier CSIC ORCID
Issue Date2012
CitationGEFES 2012
AbstractWe have prepared and deeply characterized two different bulk samples of La2MnCoO6 double perovksite. By varying the cooling rate after the final sintering temperature, we have got two different degrees of Mn/Co order (defined as the amount of Co or Mn in the corresponding crystallographic sublattice): 95 and 74%. Magnetic properties, structural behavior, dielectric anomalies and magnetodielectric response of La2MnCoO6 have been investigated by means of ultra-high resolution synchrotron X-ray powder diffraction, neutron powder diffraction (used to determine the degree of cationic order), resistivity, magnetization, and dielectric measurements. Both samples present a clean and sharp transition from a paramagnetic (PM) to a ferromagnetic (FM) state on cooling. Beside the well known influence on magnetic properties, our results show that the main effect of disorder lies on the electrical resistivity. Bond distances clearly show Mn4+/Co2+ valence states in well ordered sample and that these valences do not change across PM to FM transition. For the disordered one, this picture is compatible with experimental results. Ultra high-resolution synchrotron X-ray powder diffraction demonstrates that PM to FM transition takes place with no magnetostriction effect, in contrast with other double perovskites showing dielectric anomalies. AC-data evidence dielectric anomalies and a small magnetodielectric effect, but impedance complex plane analyses prove that these phenomena appear at the frequency-temperature region where extrinsic effects dominate the dielectric response.
DescriptionResumen del póster presentado a la VII Reunión Grupo Especializado de Física de Estado Sólido celebrado en Sevilla (España) del 25 al 27 de enero de 2012.
Appears in Collections:(ICMA) Comunicaciones congresos
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