Figure 1

Temperature dependence of the 200 Bragg reflection for (a) $x=0.325$ and (b) $x=0.460$. Shown are the integrated intensity, full-width-at-half-maximum (FWHM), and peak position (${\omega }_s$) of Gaussian fits to rocking (transverse) scans through the Bragg peak. Also shown is the average unit cell volume (aristotype) determined from Gaussian fits to radial scans through the Bragg peak. Apparent phase transition temperatures are marked by dashed lines. Error bars correspond to uncertainties of $1\sigma$ in the fitted parameters. Measurements were performed on BT-9 with horizontal beam collimations of 40’-47’-40’-80’ and a single PG filter.Reuse & Permissions

Figure 2

(a)–(c) Radial scans through the $X$, $M_1$, and $M_2$ points reveal no superlattice reflections for $x=0.325$ at 35 K. (d) Scans through one $R_2$ point at various temperatures for $x=0.325$. (e) Scans performed using two wavelengths through an $R_1$ point for $x=0.325$. (f) The order parameters of the superlattice phases are given by the peak intensity of the $\frac{5}{2}\frac{1}{2}\frac{1}{2}$ reflection. Error bars represent an uncertainty of $1\sigma$ in the measured intensities. Scans in (a)–(d) and (f) were made using collimations of 40’-47’-40’-80’, 3 PG filters, and $\lambda =2.359\AA$ on BT-9. The scans in (e) were made on SPINS with collimations of 80’-80’ and two Be filters.Reuse & Permissions

Figure 3

(a) Radial scans through the 200 Bragg reflection of the $x=0.325$ crystal at selected temperatures. The measurements were performed on BT-9 with $\lambda =2.359\AA$, collimations of 15’-47’-10’-20’, a single PG filter, and the Ge 220 analyzer. Also shown is a measurement of single crystal ${\mathrm{SrTiO}}_3$ (data from Ref. 24 represented by green triangles) obtained with collimations of 10’-40’-20’-40’. (b) Radial scans through 200 for the $x=0.460$ crystal using the PG 002 analyzer, 3 PG filters, and collimations of 15’-10’-10’-10’.Reuse & Permissions

Figure 4

High resolution radial scans performed through the $R_2$ point on SPINS using collimations of G (39’)-40’-10’-20’, two Be filters, and with $\lambda =4.045\AA$.Reuse & Permissions