Strong bulk Dzyaloshinskii-Moriya interaction in composition-uniform centrosymmetric magnetic single layers

Abstract: Dzyaloshinskii-Moriya interaction (DMI) is the key ingredient of chiral spintronic phenomena and the emerging technologies based on such phenomena. A nonzero DMI usually occurs at magnetic interfaces or within non-centrosymmetric single crystals. Here, we report the observation of a strong unexpected DMI within a centrosymmetric polycrystalline ferromagnet that has neither a crystal inversion symmetry breaking nor a composition gradient. This DMI is a bulk effect, increases with the thickness of the magnetic layer, and is insensitive to the symmetry of the interfaces or the neighboring materials. We observe a total DMI strength that is a factor of >2 greater than the highest interfacial DMI in the literature. This DMI most likely arises from the strong spin-orbit coupling, strong orbital hybridization, and a "hidden" long-range asymmetry in the material. Our discovery of the strong unconventional bulk DMI in centrosymmetric, composition-uniform magnetic single layers provide fundamental building blocks for the emerging field of spintronics and will stimulate the exploitation of unconventional spin-orbit phenomena in a wide range of materials.