Magnetic structure of ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$

${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ crystallizes in the orthorhombic space group $Pnma$, and orders antiferromagnetically below the Néel temperature $T_N\sim 127\mathrm{K}$. We have employed x-ray resonant magnetic scattering to elucidate the details of the magnetic structure. The magnetic unit cell is the same as the chemical unit cell. From azimuth scans and the $\mathbf{Q}$ dependence of the magnetic scattering, all three Gd sites in the structure were determined to be in the same magnetic space group $Pn{m}^{\prime }a$. The magnetic moments are primarily aligned along the $\mathbf{c}$ axis and the $\mathbf{c}$ components of the magnetic moments at the three different sites are equal. The ferromagnetic Gd-rich slabs are stacked antiferromagnetically along the $\mathbf{b}$ direction.

Figure 1

The crystal structure of ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$. Shaded regions indicate the Gd-rich “slabs” stacked along the $\mathbf{b}$ direction.

Figure 2

Magnetic susceptibility $M∕H$ of the ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ single crystal. The temperature dependence of the susceptibility was measured on heating of the zero-field cooled sample in a field of $100\mathrm{Oe}$ applied parallel to the three crystallographic axes.

Figure 3

(a) Contour map of the intensity as a function of energy and azimuth angle $\psi$ at the (5 0 0) position and $T=8\mathrm{K}$. Discontinuities in the bands of multiple scattering across the energy range are artifacts of the scanning process and (b) single energy scan at the azimuth angle $\psi =59.9°$, which is depicted as a horizontal dashed line in (a). In (b), the vertical dashed line represents the position of the Gd $L_{\mathrm{II}}$ absorption edge.

Figure 4

(a) $\theta$ scan through the (0 3 0) magnetic peak at $10\mathrm{K}$ (filled circles) and $145\mathrm{K}$ (open circles) and (b) energy scans at $10\mathrm{K}$ (filled circles) and $145\mathrm{K}$ (open circles) through the magnetic peak. The data were measured at an azimuth angle of $\psi =30°$ using aluminum attenuator with 0.41 transmission. The dashed line represents the position of the Gd $L_{\mathrm{II}}$ absorption edge.

Figure 5

(a) Integrated intensity of the (0 7 0) magnetic peak measured upon heating the sample, at an azimuth angle of $\psi =30°$, using an aluminum attenuator with 0.41 transmission. (b) Integrated intensity of the (5 0 0) resonant peak measured during heating at an azimuth angle of $\psi =60°$ without attenuator.

Figure 6

The integrated intensity of the (0 3 0) magnetic peak normalized by the (0 4 0) charge peak at $T=8\mathrm{K}$. The solid curve represents the variation expected for magnetic moments along the $\mathbf{c}$ axis.