Abstract
Controlling electronic transport through a single-molecule junction is crucial for molecular electronics or spintronics. In magnetic molecular devices, the spin degree-of-freedom can be used to this end since the magnetic properties of the magnetic ion centers fundamentally impact the transport through the molecules. Here we demonstrate that the electron pathway in a single-molecule device can be selected between two molecular orbitals by varying a magnetic field, giving rise to a tunable anisotropic magnetoresistance up to 93%. The unique tunability of the electron pathways is due to the magnetic reorientation of the transition metal center, resulting in a re-hybridization of molecular orbitals. We obtain the tunneling electron pathways by Kondo effect, which manifests either as a peak or a dip line shape. The energy changes of these spin-reorientations are remarkably low and less than one millielectronvolt. The large tunable anisotropic magnetoresistance could be used to control electronic transport in molecular spintronics.
Highlights
Controlling electronic transport through a single-molecule junction is crucial for molecular electronics or spintronics
The FePc molecule belongs to a class of planar metal–phthalocyanine molecules, which have an indispensable role in spintronic applications due to the wide range of tunability of the spin-bearing centers[1,15,16,17,18,19,20]
After adsorption on Au(111), the FePc molecule appears in scanning tunneling microscope (STM) images as a cross with a central protrusion (Fig. 2a)
Summary
Controlling electronic transport through a single-molecule junction is crucial for molecular electronics or spintronics. We demonstrate that the electron pathway in a single-molecule device can be selected between two molecular orbitals by varying a magnetic field, giving rise to a tunable anisotropic magnetoresistance up to 93%. The interaction of the magnetic molecules with a metal substrate can lead to a collective quantum behavior, such as the Kondo effect in which the spin moment is screened by the coherent spin–flip process of the conduction electrons, giving rise to a Kondo resonance at the Fermi level (EF)[10,21]. We use the line shape and spatial distribution of the Kondo resonance of FePc as indicators to monitor the electron pathway in the tip–FePc–Au junction and demonstrate that the electrons travel through the FePc by two possible d orbitals: dz[2] and dπ (dπ represents dxz or dyz), and that the single-electron passage through the FePc can be controlled by the external magnetic field (Fig. 1). Density functional theory (DFT) calculations reveal that this unique tunability originates from the reorientation of the magnetic moment on the Fe atom
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