High-Quality CrO_{2} Nanowires for Dissipation-less Spintronics

Abstract

Superconductor-ferromagnet (S-F) hybrids based on half-metallic ferromagnets, such as CrO_{2}, are ideal candidates for superconducting spintronic applications. This is primarily due to the fully spin-polarized nature of CrO_{2}, which produces enhanced long-range triplet proximity effects. However, reliable production of CrO_{2}-based Josephson junctions (JJs) has proved to be extremely challenging because of a poorly controlled interface transparency and an incomplete knowledge of the local magnetization of the CrO_{2} films. To address these issues, we use a bottom-up approach to grow CrO_{2} nanowires on prepatterned substrates via chemical-vapor deposition. A comprehensive study of the growth mechanism enables us to reliably synthesize faceted, homogeneous CrO_{2} wires with a well-defined magnetization state. Combining these high-quality wires with a superconductor produces JJs with a high interface transparency, leading to exceptionally large 100% spin-polarized supercurrents, with critical current densities exceeding 10^{9} Am^{-2} over distances as long as 600 nm. These CrO_{2}-nanowire-based JJs thus provide a realistic route to creating a scalable device platform for dissipation-less spintronics.