Polarisationsschwankungen eines Ferroelektrikums in der Umgebung eines Umwandlungspunktes zweiter Art (Curie-Punkt)

Abstract

The polarization fluctuations of Rochelle salt monocrystals were measured as noise voltage across the plates of a condensor, filled with this material. In every case studied the behaviour is quantitative given byNyquist's formula. Critical polarization fluctuations, a typical nonlinear phenomenon, which are expected at the ferroelectric transition point of second order in analogy to density fluctuations at the critical point of gases could not be observed. At audio frequencies the noise is essentially influenced by the relaxation of certain lattice defects. The possibility of measuring critical polarization fluctuations is discussed. It is pointed out, that the conditions which will permit to observe critical fluctuations, could hardly be realized.