2003/01/30 by J M Mart n-Olalla, J. M. Martin-Olalla, F. J. Romero +7
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Solid-state spectroscopy and crystallography #Theoretical and Computational Physics #cond-mat
paper · pdf · doi:10.1088/0953-8984/15/14/318
published as Journal of Physics: Condensed Matter 15(14) 2423-2434 (2003) · 13 pp. 9 ff. 2 tab. RevTeX. Submitted to J. Phys.: Cond. Matter
arxiv created 2003/01/30 · openalex publication_date 2003/03/31 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
Asymptotic behaviour near phase transitions can be suitably characterized by the scaling of Δ s / Q 2 with = 1 − T / T c , where Δ s is the excess entropy and Q is the order parameter. As Δ s is obtained by integration of the experimental excess specific heat of the transition Δ c , it displays little experimental noise so that the curve log(Δ s / Q 2 ) versus log is better constrained than, say, log Δ c versus log . The behaviour of Δ s / Q 2 for different universality classes is presented and compared. In all cases, it clearly deviates from being a constant. The determination of this function can then be an effective method to distinguish asymptotic critical behaviour. For comparison, experimental data for three very different systems, Rb 2 CoF 4 , Rb 2 ZnCl 4 and SrTiO 3 , are analysed under this approach. In SrTiO 3 , the function Δ s / Q 2 does not deviate within experimental resolution from a straight line so that, although Q can be fitted with a non mean-field exponent, the data can be explained by a classical Landau mean-field behaviour. In contrast, the behaviour of Δ s / Q 2 for the antiferromagnetic transition in Rb 2 CoF 4 and the normal–incommensurate phase transition in Rb 2 ZnCl 4 is fully consistent with the asymptotic critical behaviour of the universality class corresponding to each case. This analysis therefore supports the claim that incommensurate phase transitions in general, and the A 2 BX 4 compounds in particular, in contrast with most structural phase transitions, have critical regions large enough to be observable.