Spin-Density-Wave Transition in Dilute YGd Single Crystals

Neutron diffraction, heat capacity, and susceptibility measurements on dilute YGd single crystals (1.5 to 4.4 at.% Gd) show long-range helical magnetic ordering at low temperatures. A periodic incommensurate spin structure with the Gd moments in the basal plane and a propagation wave vector of ${0.28c}^{*}$ is found. A semicusplike behavior is observed in the magnetic specific heats with the maxima at similar temperatures as the susceptibility $\frac{d\left(\mathrm{XT}\right)\mathrm{}}{\mathrm{dT}}$ peaks $\mathrm{H}\perp \mathrm{c}$ axis) and the onset of Bragg scattering. These results are quantitatively interpreted within a helical spin-density-wave stabilization of the conduction electrons.