Helical Magnetic Order and Spin Slips in Holmium-Yttrium Superlattices

The chemical and magnetic structures of a series of Ho/Y superlattices have been studied using X-ray and neutron scattering techniques. The X-ray diffraction results show that the superlattices have a high degree of crystalline order, with sharp interfaces between the two materials. From the neutron scattering the Ho 3+ magnetic moments are found to form a basal-plane helic at all temperatures in the ordered phase, with an apparent suppression of the low-temperature cone base. The chirality of the helix is coherently maintained across the yttrium with an effective, temperature-independent turn angle of 51.1(1.5)°. Below ≈ 30 K the Ho 3+ moments form commensurate spin-slip structures.