Emergent Spin Ordering at C60 interfaces

This work is a pioneer study on the role played by molecular interfaces in altering the electronic states of non-ferromagnetic materials. Here, we consider diamagnetic copper and paramagnetic manganese and scandium, to overcome the Stoner criterion and make them magnetically ordered at room temperature. The mechanism is mediated by the charge transfer from the transition metal and hybridization with molecular carbon, creating new 3d-π that drastically modify the electron energy bands around the Fermi energy of both metal and molecule. This effect is achieved via interfaces between metallic thin films and C60 molecular layers. The emergent spin ordering arising in these systems is measured using magnetometry shows magnetically ordered behaviour at room temperature, but dependent on the thickness and continuity of the metallic layer. To determine how in the layered structure the emergent spin ordering is distributed, low-energy muon spin spectroscopy is utilised by studying the depolarization process of low-energy muons implanted in the sample. This technique indicates localised spin-ordered states at, and close to, the metallo-molecular interface. X-ray absorption spectroscopy provides an excellent tool for identifying the emergent spin ordering of specific elements within a sample. The change in the molecular orbitals of C60 due to charge transfer and 3d-π hybridization is evaluated based on this technique. The presence of spin ordering in a non-magnetic metallic host due to molecular charge transfer has a drastic effect not only on the magnetic but also on the transport properties of the system. The decisive role of the molecular interfaces in the physics of spin dependent scattering within a non-magnetic host has been demonstrated. Localised spin ordering leads to changes in the Kondo and weak localisation effects with applications in low temperature thermometry and quantum devices. It is found that there is an additional magnetic scattering that has a pronounced contribution when C60 molecules are embedded into the non-magnetic Cu and hence creates localised spins. The localised spin ordering that emerged at molecular interfaces is a new approach for novel generation of materials for future spintronics devices

Emergent magnetism at transition-metal–nanocarbon interfaces

Charge transfer at metallo–molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc–C60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo–carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp3 orbitals are annealed into sp2−π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz–π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices

Data on Emergent Magnetism in Metallo-Carbon Interfaces.

Data as presented in the paper by Fatma Al Ma'Mari et al. In the journal Proceedings of the National Academy of Sciences of the United States of America vol. 114 (22), pp 5583-5588 (2017)

Data on spin-singlet to triplet Cooper pair converter interface

This dataset contains the measurements reported in the manuscript "Spin-singlet to triplet Cooper pair converter interface". In this study, we fuse magnetism and superconductivity in a system where spin-ordering and diffusion of Cooper pairs are achieved at a non-intrinsically magnetic nor superconducting Cu/C60 interface. Electron transport, magnetometry and low-energy muon spin rotation are used to probe time-reversal symmetry breaking in these structures

Spin-singlet to triplet Cooper pair converter interface

Combining magnetic and superconducting functionalities enables lower energy spin transfer and magnetic switching in quantum computing and information storage, owing to the dissipationless nature of quasi-particle mediated supercurrents. Here, we put forward a system where emergent spin-ordering and diffusion of Cooper pairs are achieved at a non-intrinsically magnetic nor superconducting metallo-molecular interface. Electron transport, magnetometry and low-energy muon spin rotation are used to probe time-reversal symmetry breaking in these structures. By comparing the Meissner expulsion in a system including a Cu/C60 spin-converter interface to one without, we observe a paramagnetic contribution that can be explained due to the conversion of spin-singlet Cooper pair states into odd-frequency triplet states. These results demonstrate the potential of metallo-molecular interfaces to achieve singlet to triplet Cooper pair conversion, a capability not present in either metal or molecule separately that could be used in the generation and controlled diffusion of spin polarised dissipationless currents