Large Magnetoresistance at Room Temperature in Organic Molecular Tunnel Junctions with Nonmagnetic Electrodes.
We report room-temperature resistance changes of up to 30% under weak magnetic fields (0.1 T) for molecular tunnel junctions composed of oligophenylene thiol molecules, 1-2 nm in length, sandwiched between gold contacts. The magnetoresistance (MR) is independent of field orientation and the length of the molecule; it appears to be an interface effect. Theoretical analysis suggests that the source of the MR is a two-carrier (two-hole) interaction at the interface, resulting in spin coupling between the tunneling hole and a localized hole at the Au/molecule contact. Such coupling leads to significantly different singlet and triplet transmission barriers at the interface. Even weak magnetic fields impede spin relaxation processes and thus modify the ratio of holes tunneling via the singlet state versus the triplet state, which leads to the large MR. Overall, the experiments and analysis suggest significant opportunities to explore large MR effects in molecular tunnel junctions based on widely available molecules.
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Zuoti
Z
Xie
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Sha
S
Shi
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Feilong
F
Liu
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Darryl L
DL
Smith
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
P Paul
PP
Ruden
Department of Chemical Engineering and Materials Science and ‡Department of Electrical and Computer Engineering, University of Minnesota , Minneapolis, Minnesota 55455, United States.
C Daniel
CD
Frisbie
charge transport; interface dipole; magnetoresistance; singlet and triplet transmission; tunneling molecular junction; unpaired charge carrier