Optimization of magnetic reference layer for neutron reflectometry.

Neutron reflectivity is a powerful technique for probing density profiles in films, with applications across physics, chemistry and biology. However, challenges arise when dealing with samples characterized by high roughness, unknown scattering length density (SLD) with low contrast, very thin layers or complex multi-layered structures that cannot be uniquely resolved due to the phase problem. Incorporating a magnetic reference layer (MRL) and using polarized neutron reflectivity improves the sensitivity and modelling accuracy by providing complementary information. In this study, we introduce a quantitative means of comparing MRL systems in a model-free way. We apply this approach to demonstrate that CoTi alloys offer a superior solution as MRLs compared with the commonly used Fe or Ni MRLs. The low nuclear and magnetic scattering length densities of CoTi significantly enhance sensitivity, making it particularly advantageous for soft-matter research. Furthermore, the tunable Co versus Ti ratio allows for optimization of the SLD to achieve maximum sensitivity, establishing CoTi as a highly effective choice for MRL applications. The applied simulation framework for optimizing MRL sensitivity to a specific materials system and research question is a generic approach that can be used prior to growing the MRL for a given experiment.