Figure 1

Temperature dependence of the specific heat. $T_{N1}$ and $T_{N2}$ are the spontaneous magnetic ordering temperatures of the Fe and Sm magnetic moments respectively. $T_S$ is the structural phase transition temperature. Vertical lines are guides to the eye after x-ray diffraction measurements.Reuse & Permissions

Figure 2

(a) Temperature dependence of the magnetic susceptibility measured upon heating of the zero-field cooled sample in a field of 1 T. (b) $M$-$H$ curves for magnetic fields parallel and perpendicular to the $c$ direction at several temperatures.Reuse & Permissions

Figure 3

(a) Temperature dependence of the orthorhombic distortion. Inset shows ($\xi$ 0 0) scans through the (4 0 6) reflection. (b) Temperature dependence of the (1 0 6.5) reflection measured in both resonant (at $E=7.106$ keV, which is 6 eV below the Fe $K$-edge energy of 7.112 keV) and nonresonant (100 eV below the Fe $K$ edge) conditions at P09 with a displex. Lower inset shows temperature dependence of the (1 0 6.5) reflection measured using the cryomagnet. All other measurements below 5 K were performed using the orange cryostat. Upper inset shows rocking scans at the (3 0 7.5) and (0 3 7.5) reflections at selected temperatures. (c) Temperature dependencies of the (3 0 7.5) and ($-$2 0 6) reflections measured in resonant condition ($E=7.314$ keV) at the Sm $L$${}_2$ edge. Open (closed) circles represent measurements with (without) attenuation of the primary beam. Solid thin lines serve as guides to the eye while thick lines (red) show fit as described in the text.Reuse & Permissions

Figure 4

(a), (b), (d), (e) Energy scans of the (1 0 7.5), (0 1 7.5), and ($-$2 0 6) reflections and of the absorption coefficient at the Sm $L$${}_2$ (left panel) and $L$${}_3$ edges (right panel). The dashed lines depict the Sm $L$${}_2$ and $L$${}_3$ absorption edges as determined from the inflection point of the absorption coefficient. The absorption coefficient was calculated and the intensity was corrected following the recipe described in Refs. 19 and 20. (c) Energy scans of the absorption coefficient and of the (1 0 6.5) reflection below ($T=55$ K, filled circles) and above ($T=112$ K, open squares) $T_{N1}$, and the measured background at $T=55$ K away from the magnetic Bragg peak (open circles). The dashed line depicts the Fe $K$ edge. (f) Comparison of the temperature dependences of the dipole and quadrupole resonances for the ($-$2 0 6) and (1 0 7.5) reflections, respectively. For the ($-$2 0 6) reflection, integrated intensity was measured approximately 30 eV below (off-resonance, O-R) the observed resonance (R, $E=6.710$ keV and 7.314 keV for the Sm $L$${}_3$ and $L$${}_2$ edges, respectively) to show the temperature dependence of the pure charge signal. The intensities have not been corrected for absorption. In (a)–(e), vertical arrows indicate the energies at which temperature dependences of the resonant signal were measured for Figs. 3b and 3c and Fig. 4f. In (a)–(f), lines serve as guides to the eye.Reuse & Permissions

Figure 5

(a) $l$ dependence of the integrated intensity at the Sm $L$${}_2$ edge along with the fits for the (1 0 $\frac{l}{2}$) reflections. Open symbols are the calculated intensities. Lines serve as guides to the eye. (b) Proposed magnetic structure in the temperature range $5\text{K}\le T\le 110\text{K}$.Reuse & Permissions

Figure 6

(a) and (b) $l$ and $h$ scans through the (1 0 6.5) reflection. $10\%$ of the incident beam was used to reduce the sample heating. For comparison, scans at $T=4.5$ K is plotted together with scans taken at $T=2.0$ K. We noticed that the sample heating is much greater in the cryomagnet than in the orange cryostat. The remaining intensity at $T=2$ K is due to the residual sample heating in the cryomagnet.Reuse & Permissions

Figure 7

Rocking scans through the (1 0 7) reflection in both the $\pi \to \sigma$ and $\pi \to \pi$ channels. Higher background in the $\pi \to \pi$ channel is mainly due to the less suppression of the fluorescence background.Reuse & Permissions