Magnetic waveguides for neutron reflectometry

Abstract

We show that the sensitivity and depth selectivity of neutron reflectometry can be greatly enhanced through a waveguide design that takes advantage of the spin-dependent magnetic neutron scattering potential to steer spin-up and spin-down neutrons into waveguide modes with different depth profiles. Using a bilayer of manganate and ruthenate ferromagnets, we demonstrate that a magnetic waveguide structure with sharp spin-up and spin-down modes centered in the two different layers can be generated by adding a magnetically inactive capping layer. The resulting reflectometric data allow accurate and reliable determination of a small in-plane magnetization in the ruthenate layer, despite its immediate proximity to the manganate layer with much larger magnetization. Magnetic neutron waveguides thus enable depth-sensitive measurements of small electronic spin polarizations in a large variety of magnetic multilayers and devices.