Heteronuclear Metalloporphyrin Dimers for Molecular Spintronics

Lead Research Organisation: University of Oxford
Department Name: OxICFM CDT

Abstract

A spin valve is an electronic device that can switch between two states - one of low resistance and one of high resistance - in response to an external magnetic field. Spin valves have played an important role in shaping the information technology landscape since their first development in the late 1980s by dramatically increasing magnetic data storage capacities with applications as read heads in hard disc drives (HDD), magnetic sensors, and memory unit in magnetic random-access memories (MRAM). The development of spin valves is part of the research field of spintronics - short for spin electronics - which comprises devices that make use of the charge and spin of electrons. Spin is a quantum-mechanical property that takes two discrete values: spin-up or spin-down.
Traditional spin valves are three-layer devices in which two conductive magnetic layers are separated by a non-magnetic layer. If the magnetic moments of the two magnetic layers point in the same direction, the resistance of the device is low, which results in a high electric current. If the two magnetic moments point in opposite directions, the resistance increases leading to a smaller electric current. This behaviour is caused by the spin polarization of the electrons of the electric current when passing through the magnetic layers: all electron spins are oriented either "up" or "down" depending on the magnetic orientation of the layer. Only if the two magnetic layers favour the same spin polarization, electrons can travel though the device efficiently leading to the low resistance state and the generation of a net spin polarized current.
The relative orientation of the two magnetic moments can be changed by applying an external magnetic field. This allows for the magnetoresponsive switching between an on-state with high conductance and a low conductance off-state. The translation of changes in the magnetic environment into electronic information is the key concept behind the broad range of application of spin valves.
This project targets the rational design, synthesis and study of the electronic properties of a single-molecule spin valve. Individual molecules are the smallest stable structural building blocks with only a few nanometres in size. Therefore, the design of functional molecules that mimic the properties of macroscopic electronic components is fundamental for the ultimate miniaturization of electronic circuits to the nanometre scale. To date, such molecular circuits have been elusive, but the continuous demand for increasing computing powers and the inherent limits of present manufacturing techniques make the transition to a molecular electronics landscape highly desirable.
Our approach for the synthesis of a single-molecule spin valve is based on the combination of two molecular magnets and a conductive wire in a single molecule. The molecular magnets will generate a spin polarization in the current passing through the wire and - analogous to a traditional spin valve - both magnetic centres need to favour the same spin orientation to result in a strong current through the device. The realization of a single-molecule spin valve is an important step towards understanding fundamental structure property relationships in the design of molecular electronic devices. It also has potential applications as a magnetoresponsive switch in a molecular circuit and for the generation of spin polarized currents for the use in molecular quantum information storage and quantum computing.
This multidisciplinary project involves a wide range of techniques including chemical synthesis, theoretical modelling, spectroscopic measurements, magnetometry, and cryogenic charge transport measurements. The project falls within the EPSRC quantum technologies research area and is conducted in close collaboration between the Department of Chemistry and the Department of Materials at the University of Oxford.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023828/1 01/04/2019 30/09/2027
2329443 Studentship EP/S023828/1 01/10/2019 30/09/2023 Sebastian Kopp