Magnetoresistance in Co-hBN-NiFe tunnel junctions enhanced by resonant tunneling through single defects in ultrathin hBN barriers

Abstract

Hexagonal boron nitride (hBN) is a prototypical high-quality two-dimensional insulator and an ideal material to study tunneling phenomena, as it can be easily integrated in vertical van der Waals devices. For spintronic devices, its potential has been demonstrated both for efficient spin injection in lateral spin valves and as a barrier in magnetic tunnel junctions (MTJs). Here we reveal the effect of point defects inevitably present in mechanically exfoliated hBN on the tunnel magnetoresistance of Co-hBN-NiFe MTJs. We observe a clear enhancement of both the conductance and magnetoresistance of the junction at well-defined bias voltages, indicating resonant tunneling through magnetic (spin-polarized) defect states. The spin polarization of the defect states is attributed to exchange coupling of a paramagnetic impurity in the few-atomic-layer thick hBN to the ferromagnetic electrodes. This is confirmed by excellent agreement with theoretical modelling. Our findings should be taken into account in analyzing tunneling processes in hBN-based magnetic devices. More generally, our study shows the potential of using atomically thin hBN barriers with defects to engineer the magnetoresistance of MTJs and to achieve spin filtering, opening the door towards exploiting the spin degree of freedom in current studies of point defects as quantum emitters.

References in corpus (18)

• Van der Waals heterostructures
• Boron nitride substrates for high-quality graphene electronics
• Electrical Control of 2D Magnetism in Bilayer CrI3
• Atomically thin boron nitride: a tunnelling barrier for graphene devices
• Very Large Tunneling Magnetoresistance in Layered Magnetic Semiconductor CrI${}_3$
• Electronic Properties of Graphene Encapsulated with Different Two-Dimensional Atomic Crystals
• Graphite and graphene as perfect spin filters
• Magnon-assisted tunnelling in van der Waals heterostructures based on CrBr3
• Spin flip scattering in magnetic junctions
• Bias induced up to 100% spin-injection and detection polarizations in ferromagnet/bilayer-hBN/graphene/hBN heterostructures
• Theory of proximity-induced exchange coupling in graphene on hBN/(Co, Ni)
• Magnetoresistance of vertical Co-graphene-NiFe junctions controlled by charge transfer and proximity-induced spin splitting in graphene
• Tunnel Magnetoresistance with Atomically Thin Two-Dimensional Hexagonal Boron Nitride Barriers
• Evidence for defect-mediated tunneling in hexagonal boron nitride-based junctions
• Phonon-assisted resonant tunneling of electrons in graphene-boron nitride transistors
• Resonant Spin-Dependent Tunneling in Spin-Valve Junctions in the Presence of Paramagnetic Impurities
• A spintronic source of circularly polarized single photons
• Bias dependence of tunneling magnetoresistance in magnetic tunnel junctions with asymmetric barriers

Cited by in corpus (5)

• Colloquium: Spintronics in graphene and other two-dimensional materials
• Tunnel spectroscopy of localised electronic states in hexagonal boron nitride
• Tunneling spectroscopy as a probe of fractionalization in 2D magnetic heterostructures
• Substitutional Si impurities in monolayer hexagonal boron nitride
• Charge transfer due to defects in hexagonal boron nitride/graphene heterostructures: an ab initio study