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2D magnetic materials for molecular SPINtronics

Periodic Reporting for period 1 - 2DSPIN (2D magnetic materials for molecular SPINtronics)

Período documentado: 2018-01-01 hasta 2019-12-31

Spintronics, which aims at using the spin state of electrons to process information, is a promising route to supplement conventional electronics. The field is rapidly diversifying into Molecular Spintronics where magnetic molecules are the core of the devices and Organic Spintronics where spin currents are injected from ferromagnetic metals into organic materials like graphene. The electrical control of the molecular magnetism and the spin injection are however still limited and not well understood. The aim of 2DSPIN is to push Spintronics beyond the state-of-the-art by merging new magnetic 2D materials with magnetic molecules (0D) in hybrid mixed-dimensional (0D-2D, or 0D-1D) devices. The final goal is to achieve a full control over the spin of individual molecules by injecting spin polarized currents from all-2D devices.

The achievement of (a) enhanced spin injection and thereafter (b) the electrical control of spin of individual magnetic molecules could be ground-breaking for the development of new electronics and spintronics devices based on the emerging mixed dimensional van der Waals structures (2D material-molecules). These might reach
beyond the limits of current CMOS and silicon-based technologies. 2DSPIN also replaces conventional magnetic metals, like Ni or Co, as spin injectors. The understanding of 2D material/molecules magnetic hybrids will, in the short term, optimize existing spintronics prototypes. In the long term, it maycatalyse a new generation of high-performance, cost effective and low-power consuming electronic devices based on molecules. These devices have potential to be applied in a broad number of technological and societal fields like, high density data storages, microelectronics, (bio)sensors, quantum computing and medical technologies, with the associated impact in society.
During 2DSPIN we have implemented a liquid-phase exfoliation technique that allows us to obtain hundreds of flakes in organic suspensions. We have applied this method to exfoliate two naturally occurring van der Waals heterostructures: franckeite and cylindrite. The structural characterization shows that the flakes preserve their structure down to the 2D limit. In addition, the magnetic characterization shows that cylindrite presents magnetic interactions down to the 2D limit. Cylindrite is therefore a good candidate to use in 2D spintronics. In a further step, we have fabricated nanoscale field effect transistors based on these exfoliated materials. The nanoelectrodes are fabricated by nanolithography and the layers are positioned with nanometric precision by using a dielectrophoresis technique. In short, the generated AC field induces a dipole in the materials that are attracted into the inter-electrodes space. The electrical characterization shows that the materials behave as p-doped semiconductors.

In a second stage, we have design and fabricated mixed-dimensional molecular hybrids. In particular SCO molecules have been encapsulated within carbon nanotubes, also magnetic porphyrins have been coupled to carbon nanotubes through mechanical bonds (por-MINTs). The goal was to study how the spin state affects the transport across the carbon nanotube. We have fabricated nanodevices based on these mixed-dimensional materials. We observe how the electron transport across the tube is sensitive to the SCO transition in the molecule. On the other hand, the magnetic characterization of the porphyrin MINTs shows that the magnetic porphyrins preserve their magnetic structure when attached to the carbon nanotube. The next steps will be to integrate these molecular hybrids in between cylindrite electrodes, to combine the magnetism of the electrodes with the magnetism of the hybrid.

Finally, we are working on fabricating heterostructures between the magnetic cylindrite and the non-magnetic graphene. The initial characterization shows a slight doping of graphene due to the presence of the van der Waals heterostructure.
The research developed during 2DSPIN has introduced a new promising family of 2D magnetic and conducting materials. The combination of dielectrophoresis and liquid-phase exfoliation will facilitate the fabrication of large scale devices based on 2D magnetic materials.

Another breakthrough of 2DSPIN is the fabrication and characterization of new concepts of supramolecular magnetic materials. The new designs proposed in 2DSPIN provides robust hybrids where magnetic molecules are coupled to good electric conductors (the carbon nanotubes) without altering the transport properties. The transport across the carbon nanotube is sensitive to the spin state of the SCO. This effect has not been observed before in 1D/0D magnetic hybrids.
Franckeite field-effect transistor