High-Quality CrO2 Nanowires for Dissipation-less Spintronics

Amrita Singh,Kaveh Lahabi,Charlotte Jansen,Jan Aarts

doi:10.1103/physrevx.6.041012

Abstract

Superconductor-ferromagnet (S-F) hybrids based on half-metallic ferromagnets, such as CrO2, are ideal candidates for superconducting spintronic applications. This is primarily due to the fully spin-polarized nature of CrO2, which produces enhanced long-range triplet proximity effects. However, reliable production of CrO2-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 CrO2 films. To address these issues, we use a bottom-up approach to grow CrO2 nanowires on prepatterned substrates via chemical-vapor deposition. A comprehensive study of the growth mechanism enables us to reliably synthesize faceted, homogeneous CrO2 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 109 Am−2 over distances as long as 600 nm. These CrO2-nanowire-based JJs thus provide a realistic route to creating a scalable device platform for dissipation-less spintronics.Received 29 June 2016DOI:https://doi.org/10.1103/PhysRevX.6.041012Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasOdd-frequency superconductivityCondensed Matter, Materials & Applied Physics

Highlights

Ferromagnetic nanostructures have emerged as a leading candidate for spintronic applications because of their ability to carry spin-polarized currents [1,2]
One of the biggest challenges facing the field of spintronics is the large amount of dissipation that is generated by current-driven processes at the nanoscale [3,4]
Since triplet Cooper pairs are not affected by the exchange field of the ferromagnet, they can survive over considerably long distances, thereby giving rise to spin-polarized supercurrents

Summary

INTRODUCTION

Ferromagnetic nanostructures have emerged as a leading candidate for spintronic applications because of their ability to carry spin-polarized currents [1,2]. Half-metallic ferromagnets are fully spin polarized and are expected to enhance the generation of triplet Cooper pairs [18], making them an ideal material choice for dissipation-less spintronics. This idea is supported by experimental studies of CrO2, a well-known halfmetallic ferromagnet. By studying the effects of confinement, growth time, and crystal orientation on the magnetic and structural morphology of these structures, we demonstrate the reliable growth of homogeneous, crystalline nanowires with a desired geometry and magnetization state This robust control over the magnetization and transparency enables us to reproducibly fabricate CrO2-based JJs with record-high critical current

Published by the American Physical Society

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