Microwave Absorption in Cubic Strontium Titanate

Abstract

An analysis of the temperature dependence of the microwave loss in SrTiO/ sub 3/ is presented using the linear chain model of a ferroelectric, It is shown that a plausible explanation of the temperature dependence of the microwave loss tangent above liquid air temperature is possible if the loss due to the damping of a virtual excitation in the wing of a fundamental lattice absorption is considered. The fundamental lattice absorption is associated with a lowfrequency ferroelectric'' transverse optical mode of the material. The microwave loss tangent can be expressed by tan delta = (T - T/aub c/)- (A + BT + DT/sub 2/). The parameter A is a measure of the damping due to the presence of imperfections in the lattice. The parameters B and D arise from damping due to three- and four- phonon processes whose origin is attributed to the anharmonic interactions of the lattice. (auth)