An optimized growth model for Fe/Pt heteroepitaxy by computational and structural studies

Thin layers of ferromagnetic/non-magnetic bimetallic heterostructures have become the focal point of spintronics, primarily due to their capacity to convert spin to charge current, leveraging the spin- and inverse spin Hall effects. However, the interfacial properties and morphologies can significantly influence this conversion. Hence, we employed molecular dynamics calculations to model the construction of the Fe/Pt interface at various bilayer growth temperatures and Pt deposition rates. We then experimentally evaluated the modeling using x-ray methods to resolve the chemical and structural state of the interface. The calculations revealed moderate diffusive phenomena between the adjacent layers and an interfacial roughness of less than 1 nm, consistent with the experimental observations. In cases where plastic relaxation of the Fe/Pt interface is insufficient, lattice deformation is mitigated by a local pseudomorphic growth caused by transformation of the Pt crystal symmetry. Additionally, interfacial planar defects may emerge as a complementary stress-relieving mechanism to misfit dislocations. By combining the experimental and computational findings, we propose optimized growth conditions for an "ideal" Fe/Pt interface, which could serve as a useful tool to control the efficiency of spin-to-charge conversion.