Experiments on multicritical points

Abstract

Crystals undergoing structural phase transitions show, under application of uniaxial stress, a rich variety of multicritical points due to symmetry breaking. Most of the results were obtained in crystals with perovskite structure which are cubic at high temperatures. This paper will review the observation of bicritical behavior in SrTiO₃ and LaAlO₃, a tetracritical point in LaAlO₃ and, most recently, [110]-stress experiments proving the cubic fixed point to be stable. Of higher sophistication are fluctuation-induced Lifshiftz tricritical behavior in RbCaF₃ and double tricritical points in KMnF₃. The possible observation of a critical end point on a first-order Potts line in SrTiO₃ and KMnF₃ is mentioned.