Perpendicular magnetic anisotropy, tunneling magnetoresistance and spin-transfer torque effect in magnetic tunnel junctions with Nb layers

TL;DR

This paper investigates Nb-based magnetic tunnel junctions, demonstrating high tunneling magnetoresistance, significant perpendicular magnetic anisotropy, and effective spin-transfer torque switching, combining superconducting properties with spintronic functionalities.

Contribution

It introduces Nb as a heavy metal layer in magnetic tunnel junctions, achieving high TMR, notable perpendicular magnetic anisotropy, and demonstrating spin-transfer torque effects in these structures.

Findings

Perpendicular magnetic anisotropy energy density of 1.85 mJ/m2

Optimized tunneling magnetoresistance of 120% at room temperature

Successful observation of spin-transfer torque switching with low current density

Abstract

Nb and its compounds are widely used in quantum computing due to their high superconducting transition temperatures and high critical fields. Devices that combine superconducting performance and spintronic non-volatility could deliver unique functionality. Here we report the study of magnetic tunnel junctions with Nb as the heavy metal layers. An interfacial perpendicular magnetic anisotropy energy density of 1.85 mJ/m2 was obtained in Nb/CoFeB/MgO heterostructures. The tunneling magnetoresistance was evaluated in junctions with different thickness combinations and different annealing conditions. An optimized magnetoresistance of 120% was obtained at room temperature, with a damping parameter of 0.011 determined by ferromagnetic resonance. In addition, spin-transfer torque switching has also been successfully observed in these junctions with a quasistatic switching current density of 7.3*10^5 A/cm2.