Abstract
We report exceptionally large tunnel magnetoresistance (TMR) for biomolecular tunnel junctions based on ferritins immobilized between Ni and EGaIn electrodes. Ferritin stores iron in the form of ferrihydrite nanoparticles (NPs) and fulfills the following roles: (a) it dictates the tunnel barrier, (b) it magnetically decouples the NPs from the ferromagnetic (FM) electrode, (c) it stabilizes the NPs, and (d) it acts as a spin filter reducing the complexity of the tunnel junctions since only one FM electrode is required. The mechanism of charge transport is long-range tunneling which results in TMR of 60 ± 10% at 200 K and 25 ± 5% at room temperature. We propose a magnon-assisted transmission to explain the substantially larger TMR switching fields (up to 1 Tesla) than the characteristic coercive fields (a few Gauss) of ferritin ferrihydrite particles at T < 20 K. These results highlight the genuine potential of biomolecular tunnel junctions in designing functional nanoscale spintronic devices.
Highlights
Charge transport through self-assembled monolayer (SAM)-based tunnel junctions generally occurs through quantum mechanical tunneling, and enables novel electronic function potentially complementary to devices based on semiconductors [1,2,3]
The measured magnetic moments in our experiments are within the range of previously reported values, whereas ferritin loaded under anaerobic conditions has a value of μB of about one order of magnitude higher than that of ferritin loaded in aerobic conditions
We have demonstrated that the tunnel magnetoresistance (TMR) characteristics of magnetic tunneling junctions based on ferritins are induced by the magnetic iron oxide core inside the ferritin
Summary
Charge transport through self-assembled monolayer (SAM)-based tunnel junctions generally occurs through quantum mechanical tunneling, and enables novel electronic function potentially complementary to devices based on semiconductors [1,2,3]. It is fundamental to efficiently inject spin-polarized carriers and transport them across the molecules inside the junctions. The resulting ferritin-based tunnel junctions display a remarkable 60% tunnel magnetoresistance (TMR) at 200 K (25% TMR at room temperature) We attribute this good TMR performance to a new mechanism of spin polarized charge transport that involves long-range tunneling across ferritin, possibly assisted by magnons excited in the ferrihydrite nanoparticles (NPs), while the protein cage efficiently decouples the magnetic ferrihydrite core from the FM bottom electrode, providing a clean tunneling barrier eliminating the need for impedance matching
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