Phase transitions in perovskites near the tricritical point: an experimental study of KMn1-xCaxF3 and SrTiO3

作者：Gallardo MC^*; Romero FJ; Hayward SA; Salje EKH; del Cerro J

来源：Mineralogical Magazine, 2000, 64(6): 971-982.

DOI：10.1180/002646100549878

• phase transition
• perovskite
• tricritical point
• Landau theory

We present experimental data for the Pm3m-I4/mcm phase transitions in the perovskite crystals KMn1-xCaxF3 and SrTiO3. Comparison of calorimetric data (latent heat and specific heat) with order parameter data (measured with X-ray rocking methods) indicates that these transitions follow mean-field behaviour, and may be described using Landau potentials where the free energy expansion includes terms up to Q(6). This potential is characteristic of transitions close to the tricritical point. Comparison of the behaviour of SrTiO3 and KMnF3 indicates that KMnF3 is closer to the tricritical point; a small amount of substitution of Ca for Mn causes the transition to cross the tricritical point from first order to second order behaviour.

• 出版日期2000-12