Spin Solar Cell Phenomenon on SMM Impacted CoFeB based Magnetic Tunnel Junctions

Published

May 31, 2023

Author(s)

Marzieh Savadkoohi, Pius Suh, Daniel Gopman, Pawan Tyagi

Abstract

Spin based photovoltaic (P.V.) effect is a novel concept in the solar energy harvesting area utilizing earth-abundant metals. Unlike previous approaches where Copper and Zinc like metals are oxidized or chemically transformed to yield a photovoltaic effect, we have utilized molecular channels to transform ferromagnetic electrodes present as the electrodes in a magnetic tunnel junction. For the first time, we demonstrated the solar cell effect on a magnetic tunnel junction where CoFeB was present on both sides of the MgO tunnel barrier. We produced cross junction shaped magnetic tunnel junction with the exposed edge with the thin film configuration as utilized to observe high tunneling magnetoresistance. We bridged single-molecule magnets (SMM) between the two CoFeB electrodes along the exposed side edges. Our SMM possessed a hexanuclear [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] [H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate] complex that is attached to alkane tethers terminated with thiols. Thiol ends of SMM formed strong chemical bonds between the two ferromagnetic electrodes to produce SMM's spin state and mediate strong exchange coupling. Contrary to conventional observation, where additional molecular channel increase conductivity between two electrodes, we observed SMM decreased the conductivity via the MTJ area. SMM impacted MTJ started exhibiting the solar cell effect. SMM impacted MTJ yielded 80 mV open circuit voltage and 10mA/Sq.cm saturation current under one sun radiation. Kelvin Probe AFM study provided direct evidence that SMM has significantly transformed the electronic properties of the thin film stack used in the MTJs. This study suggests a spin photovoltaic effect that can be observed with a very small number of molecular nanostructures impacting thin metallic films.

Citation

ACS Applied Electronic Materials

Pub Type

Journals

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Citation

Savadkoohi, M. , Suh, P. , Gopman, D. and Tyagi, P. (2023), Spin Solar Cell Phenomenon on SMM Impacted CoFeB based Magnetic Tunnel Junctions, ACS Applied Electronic Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936736 (Accessed November 26, 2025)