LOAD ORDER AND SEGREGATION PHASES: PROPERTIES MAGNETO-DIELÉCTRICASAuthor:
Rivas Murias Beatriz.
Year:
2005.
University:
A CORUÑA [
www.udc.es].
Place of defense: Facultad de Ciencias.
Place of preparation: Facultad de Ciencias.
Summary: In this Doctoral Thesis, we have focused primarily on the characterization of different dielectric compounds which have the phenomenon of mail-order loading and / or separation of phases. The work can summarize in three main sections. The first of these is devoted to a series of niquelatos laminar order to load and general formula Ln2-x Srx NiO4 (Ln = La, Pr, Nd, Sm; x = 0.33 and 0.50) First there has been a magnetic characterization and transport and subsequently we have studied their propiedade dielectric varying the method of synthesis, nature of the contact, thickness and extent of sintering samples. These studies made clear the contribution of extrinsic factors to respuest dielectric enhancing its intrinsic value. In these compounds, we have observed a connection between the state-mail presenting compounds obtained and the anomaly in the dielectric constant at temperatures linked to the order of loading. Based on these niquelatos have developed systems multilayer aislante-niquelato-aislante (insulating = mica or Teflon) with attractive values of the dielectric constant and low values of the loss tangent. In the second paragraph, we have focused on the manganita magnetorresistiva La0.67 Ca0.33 MnO3 in which we have studied their dielectric properties and the influence of external magnetic field on these properties. So in this study we obtained a significant effect magnetodieléctrico at room temperature fields and relatively low through a combination of the phenomenon of magnetorresistencia of segregation of electronic phases present in this compound and the phenomenon of polarization interfacial Maxwell-Wagner. Finally, in the last block, we have focused on the oxiboratos M2 OBO3 (M = Fe and MN), we studied its magnetic properties, transport and dielectric, in addition we also conducted and analyzed the results of electronic spin resonance. Most remarkable is the emergence of reverse magnetization in the compound of iron and in the case of oxiborato manganese, an arena where there are pairs of Zener Mn2 +-Mn3 +
