Chiral spin textures at the interface between ferromagnetic and heavy
nonmagnetic metals, such as Neel-type domain walls and skyrmions, have been
studied intensively because of their great potential for future nanomagnetic
devices. The Dyzaloshinskii-Moriya interaction (DMI) is an essential phenomenon
for the formation of such chiral spin textures. In spite of recent theoretical
progress aiming at understanding the microscopic origin of the DMI, an
experimental investigation unravelling the physics at stake is still required.
Here, we experimentally demonstrate the close correlation of the DMI with the
anisotropy of the orbital magnetic moment and with the magnetic dipole moment
of the ferromagnetic metal. The density functional theory and the tight-binding
model calculations reveal that asymmetric electron occupation in orbitals gives
rise to this correlation.