Room-temperature tunnel magnetoresistance across biomolecular tunnel junctions based on ferritin

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.We acknowledge the Ministry of Education (MOE) for supporting this research under award No. MOE2019-T2-1-137. Prime Minister's Office, Singapore under its Medium sized center program is also acknowledged for supporting this research. We kindly acknowledge the Singapore Synchrotron Light Source (SSLS) supporting our experiments at the SINS beam line under NUS core support C-380-003-003-001. We would like to acknowledge beamline scientists Dr Bruce Cowie and Dr Anton Tadich (soft x-ray (SXR) Beamline at the Australian Synchrotron) for their immense support. E d B acknowledges support from the US National Science Foundation (Grant No.: ECCS#1916874). S R acknowledges funding from CA2DM-NUS during his stay in Singapore. ICN2 is funded by the CERCA programme/generalitat de Catalunya, and the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706)