Diminished spin-flip reflectivity in stacked multilayers with varying period thicknesses of Fe/Si by incorporating 11B4C

TL;DR

This paper demonstrates that incorporating 11B4C into Fe/Si multilayers improves interface quality, reduces spin-flip scattering, and decreases internal stress, thereby enhancing neutron supermirror performance and stability.

Contribution

It introduces 11B4C co-sputtering as a method to enhance Fe/Si multilayers for neutron optics by reducing spin-flip effects and internal stress, a novel approach in this context.

Findings

Reduced spin-flip intensities in neutron reflectivity measurements.

50% reduction in internal stress of multilayers.

Enhanced reflectivity and polarization for neutron applications.

Abstract

This study investigates the effects of 11B4C co-sputtering on the structural and optical properties of Fe/Si stacked multilayers, with a focus on neutron supermirror applications. X-ray and neutron reflectivity techniques reveal that 11B4C incorporation improves interface sharpness, reduces roughness, and enhances reflectivity for all multilayer periods. Neutron reflectivity measurements show reduced spin-flip intensities, while wafer-curvature measurements indicate a 50% reduction in internal stress, allowing for higher mechanical stability of the multilayers. These improvements are attributed to the amorphization of Fe layers, which also suppress the formation of structural and magnetic domains responsible for stress and spin-flip scattering. In contrast, the pure Fe/Si sample exhibits a persistent half-order Bragg peak, indicating residual antiferromagnetic coupling. The results demonstrate that 11B4C enhances neutron optics by reducing spin-flip effects, increasing reflectivity and polarization, and alleviating stress, enabling the use of polarizers at reduced external fields compared to pure Fe/Si multilayers. These findings establish 11B4C as a transformative material for advancing neutron supermirror technology, paving the way for more efficient, stable, and high-performance polarizers in next-generation neutron optics.