晶格动力学性质对钛酸锶介电行为的影响

Effect of Lattice Dynamical Properties on Dielectric Behaviour of SrTiO_3

在105 K钛酸锶(SrTiO3)发生立方-四方的反铁畸变,对量子效应的吉布斯自由能取极小值,可得到一系列方程,原则上可以确定任意系统相变时的介电性质。研究了晶格动力学性质,特别是软模的行为,对理解介电性非常重要。介电常数完全由低频的光学声子模决定,从晶格动力学的性质出发,分析了低温时的居里-外斯定律行为。

At temperature 105 K,SrTiO3 transforms from cubic to tetragonal.Minimizing the Gibbs free energy with respect to order parameter leads to a set of equations which do,in principle,describe the dielectric behavior of any system undergoing a phase transition.To take account of quantum effects,the dielectric permittivity of SrTiO3 is measured from Gibbs free energy.The dielectric constant of SrTiO3 are closely related to its low-frequency optical phonon modes.The lattice dynamical properties,in particular the soft-mode behavior,are essential for the fundamental understanding of dielectric properties of SrTiO3 and analyzing the Curie Weiss-type law behavior at low temperature.