X-ray resonant magnetic scattering was employed to study a fully reversible spin-flop transition in orthorhombic ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ and to elucidate details of the magnetic structure in the spin-flop phase. The orientation of the moments at the three Gd sites flop 90° from the $\mathbf{c}$ axis to the $\mathbf{a}$ axis when a magnetic field, $H_{\mathrm{sf}}=9\mathrm{kOe}$, is applied along the $\mathbf{c}$ axis at $T=9\mathrm{K}$. The magnetic space group changes from $Pn{m}^{\prime }a$ to $P{n}^{\prime }{m}^{\prime }{a}^{\prime }$ for all three Gd sublattices. The magnetic anisotropy energy determined from experimental measurements is in good agreement with the calculations of the magnetic anisotropy based on the spin-orbit coupling of the conduction electrons and an estimation of the dipolar interactions anisotropy. No significant magnetostriction effects were observed at the spin-flop transition.

• Received 9 October 2007

DOI:https://doi.org/10.1103/PhysRevB.77.064425