Incommensurate Magnetic Structure in the Cubic Noncentrosymmetric Ternary Compound Pr5Ru3Al2

We performed magnetic susceptibility and neutron powder diffraction experiments on the ternary compound Pr5Ru3Al2. It belongs to the noncentrosymmetric and nonmirrorsymmetric cubic I213 space group. The previously reported ferromagnetic transition at 24 K was not detected in our improved quality samples. Instead, magnetic ordering was observed in the DC magnetic susceptibility at 3.8 K. Neutron powder diffraction further indicates that an incommensurate magnetic structure is established below 3.8 K, with the magnetic modulation vector (0.066, 0.066, 0.066) (r.l.u.). Using the magnetic representation analysis, we propose the block helical structure as a candidate for the incommensurate magnetic structure.