  Atomic-scale precision control of magnetic interactions facilitates a
synthetic spin order useful for spintronics, including advanced memory and
quantum logic devices. Conventional modulation of synthetic spin order has been
limited to metallic heterostructures that exploit RKKY interaction through a
nonmagnetic metallic spacer; however, they face problems arising from Joule
heating and/or electric breakdown. The practical realization and observation of
a synthetic spin order across a nonmagnetic insulating spacer would lead to the
development of spin-related devices with a completely different concept.
Herein, we report the atomic-scale modulation of the synthetic spiral spin
order in oxide superlattices composed of ferromagnetic metal and nonmagnetic
insulator layers. The atomically controlled superlattice exhibit an oscillatory
magnetic behavior, representing the existence of a spiral spin structure.
Depth-sensitive polarized neutron reflectometry evidences modulated spiral spin
structures as a function of the nonmagnetic insulator layer thickness.
Atomic-scale customization of the spin state could lead the field one step
further to actual spintronic applications.
