S. Asbrink et A. Waskowska, PRESSURE-INDUCED CRITICAL-BEHAVIOR OF KMNF3 CLOSE TO P-C=3.1 GPA - X-RAY-DIFFRACTION RESULTS, Physical review. B, Condensed matter, 53(1), 1996, pp. 12-15
The critical behavior of KMnF3 close to the pressure-induced cubic-to-
tetragonal structural phase transition at P-c=3.1 GPa has been studied
by single-crystal x-ray diffraction. The pressure dependence of a pri
mary order parameter has been determined from superlattice Bragg inten
sities and was found to fulfill the power law Q=A(P-P-c)(beta). The tr
ansition with a small discontinuity of the intensities close to P-c sh
ows deviations from the classical behavior similarly as in the tempera
ture-dependent transition at 186 K, where the domain structure conside
rably affects the values of the critical parameters. However, the pres
sure inhibits formation of large, single domains of definite orientati
on. Instead, increased width of diffraction profiles points to the app
earance of numerous, narrow domains which may influence the character
of the transition.