Fully Spin-transparent magnetic interfaces enabled by insertion of a paramagnetic NiO layer

TL;DR

This paper demonstrates that inserting an insulating NiO layer at Pt-based heavy metal/ferromagnet interfaces can eliminate spin backflow and spin-memory loss, significantly enhancing spin-current transmission and spin-orbit torque efficiency at room temperature.

Contribution

It introduces a method to achieve fully spin-transparent magnetic interfaces using a paramagnetic NiO layer, improving energy efficiency in spintronic devices.

Findings

Achieved dampinglike spin-orbit torque efficiency up to 0.8.

Enabled near-unity spin-current transmission at room temperature.

Provided >100 times greater energy efficiency compared to topological insulators.

Abstract

Spin backflow and spin-memory loss have been well established to considerably lower the interfacial spin transmissivity of metallic magnetic interfaces and thus the energy efficiency of spin-orbit torque technologies. Here we report that spin backflow and spin-memory loss at Pt-based heavy metal/ferromagnet interfaces can be effectively eliminated by inserting an insulating paramagnetic NiO layer of optimum thickness. The latter enables the thermal magnon-mediated essentially unity spin-current transmission at room temperature due to considerably enhanced effective spin-mixing conductance of the interface. As a result, we obtain dampinglike spin-orbit torque efficiency per unit current density of up to 0.8 as detected by the standard technology ferromagnet FeCoB and others, which reaches the expected upper-limit spin Hall ratio of Pt. We establish that Pt/NiO and Pt-Hf/NiO are two energy-efficient, integration-friendly, and high-endurance spin-current generators that provide >100 times greater energy efficiency than sputter-deposited topological insulators BiSb and BiSe. Our finding will benefit spin-orbitronic research and advance spin-torque technologies.