Incommensurate magnetic structure ofCeRhIn5

The magnetic structure of the heavy fermion antiferromagnet ${\mathrm{CeRhIn}}_5$ is determined using neutron diffraction. We find a magnetic wave vector ${\mathbf{q}}_M=(1/2,1/2,0.297),$ which is temperature independent up to $T_N=3.8\mathrm{}\hspace{0.5em}\mathrm{K}.$ A staggered moment of $0.264\left(4\right)\mathrm{}{\mu }_B$ at 1.4 K, residing on the Ce ion, spirals transversely along the c axis. The nearest-neighbor moments on the tetragonal basal plane are aligned antiferromagnetically.