Regensburg 2007 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 4: Internal Symposium “Order/Disorder versus/with Displacive Behaviour”

DF 4.6: Talk

Tuesday, March 27, 2007, 12:00–12:20, H11

Possible frustrated ferroelectricity and very high K of oxide perovskites — •Francois Gervais, Virginie Brizé, Cécile Autret, Jérôme Wolfman und Monique Gervais — LEMA UMR 6157 CNRS/CEA Universite François Rabelais Tours (France)

The integration of capacitors on silicon with the highest possible capacity per surface unit is a challenge of mobile microelectronics. One way to achieve this task is to use materials with very high dielectric constant. The origin of the dielectric constant in barium titanate takes place in displacive-order-disorder crossover mechanisms. CaCu3Ti4O12 (CCTO) opens a new way to still better properties with a dielectric constant in excess of 10,000 in the single crystal. In addition, the property little varies with temperature around room temperature. The observation of diffuse scattering in CCTO was recently observed and a frustrated ferroelectricity mechanism was proposed. When CCTO is substituted with only 0.5 % of transition metal element such as Fe or Mn, the permittivity drops down to 100, the contribution due to phonons. Electron spin resonance displays a rapid downshift of the resonance line of copper towards low magnetic field below 30 K when substituted, correlated with dielectric data. The downshift is the signature of local magnetic field. A possible multiferroic character is therefore evidenced. These results will be discussed in terms of frustrated ferroelectrics scenarios.