# Tunnel magnetoresistance of a supramolecular spin valve

## TL;DR

This paper theoretically investigates how a supramolecular spin valve's magnetoresistive properties, influenced by magnetic field and voltage tuning, depend on molecular states and transport regimes, using advanced diagrammatic techniques.

## Contribution

It introduces a theoretical analysis of a supramolecular spin valve's transport properties, highlighting the dependence on magnetic, bias, and gate voltages, and explaining the underlying molecular mechanisms.

## Key findings

- Magnetoresistance varies with magnetic field and bias voltage.
- Transport properties depend on the molecular spin state and orbital levels.
- Spin polarization of current is strongly influenced by the transport regime.

## Abstract

We theoretically study the transport properties of a supramolecular spin valve, consisting of a carbon nanotube with two attached magnetic molecules, weakly coupled to metallic contacts. The emphasis is put on analyzing the change of the system's transport properties with the application of an external magnetic field, which aligns the spins of the molecules. It is shown that magnetoresistive properties of the considered molecular junction, which are associated with changing the state of the molecules from superparamagnetic to the ferromagnetic one, strongly depend on the applied bias voltage and the position of the nanotube's orbital levels, which can be tuned by a gate voltage. A strong dependence on the transport regime is also found in the case of the spin polarization of the current flowing through the system. The mechanisms leading to those effects are explained by invoking appropriate molecular states responsible for transport. The analysis is done with aid of the real-time diagrammatic technique up to the second order of expansion with respect to tunneling processes.