Periodic Reporting for period 1 - 4f-Mag (On-surface design of lanthanide coordinated networks featuring single atom magnetism)
Reporting period: 2021-01-01 to 2022-12-31
The capacity of investigate and tailor the materials properties down to nanoscale created new perspectives for the development of functional devices using single atoms or molecules. Concerning magnetism, the stabilization of magnetic remanence in single atoms represents the ultimate limit on the size reduction of storage devices. After recent advances in this field, lanthanides have emerged as promising candidates for atomic magnets. However, the high diffusion of single standing atoms hinder the development of real-world applications. The next step to further advance towards practical devices is the coordination of these atoms in networks preserving their outstanding magnetic properties.
The 4f-Mag project consisted in the preparation of metal-organic networks by on-surface synthesis and the investigation of their structural, electronic, and magnetic properties. The main goal was to coordinate lanthanides in regular molecular arrays preserving their functionality as single atom magnets, and also enhancing their intrinsic high magnetic anisotropy and large relaxation lifetime. This project ambitioned to explore the versatility of molecular linkers to further advance in the path to accomplish single atom magnets for functional devices. The specific objectives were:
(I) Coordinate the Ln atoms using molecules to design regular arrays of single atoms.
(II) Use the coordination networks to tailor the magnetic properties and thermal stability of lanthanides atoms.
Several systems were investigated, employing molecules with different functional linkers, as carboxylic acid, phenyl, cyanamide, thiol, and hydroxyl. These molecules were coordinated with Dy and Er atoms on metallic surfaces (Au(111), Cu(111) and Ag(111)) and also on graphene/Ir(111). For some of them it was possible to successfully prepare regular networks with long-range ordering, others did not coordinate or formed irregular structures. The properties of the systems that formed regular structures were investigated. The results demonstrated that it is possible to engineer the electronic and magnetic properties of lanthanides on surfaces by coordinative protocols.
The 4f-Mag project consisted in the preparation of metal-organic networks by on-surface synthesis and the investigation of their structural, electronic, and magnetic properties. The main goal was to coordinate lanthanides in regular molecular arrays preserving their functionality as single atom magnets, and also enhancing their intrinsic high magnetic anisotropy and large relaxation lifetime. This project ambitioned to explore the versatility of molecular linkers to further advance in the path to accomplish single atom magnets for functional devices. The specific objectives were:
(I) Coordinate the Ln atoms using molecules to design regular arrays of single atoms.
(II) Use the coordination networks to tailor the magnetic properties and thermal stability of lanthanides atoms.
Several systems were investigated, employing molecules with different functional linkers, as carboxylic acid, phenyl, cyanamide, thiol, and hydroxyl. These molecules were coordinated with Dy and Er atoms on metallic surfaces (Au(111), Cu(111) and Ag(111)) and also on graphene/Ir(111). For some of them it was possible to successfully prepare regular networks with long-range ordering, others did not coordinate or formed irregular structures. The properties of the systems that formed regular structures were investigated. The results demonstrated that it is possible to engineer the electronic and magnetic properties of lanthanides on surfaces by coordinative protocols.
Several different molecular linkers were tested. These molecules were coordinated with Dy and/or Er atoms on metallic substrates and graphene. The structure of the systems was investigated by scanning tunneling microscopy (STM). In some cases it was not possible to coordinate and/or form regular networks. This possibility was considered in the project and the contingency plan was applied with the use of different molecules and substrates. It was possible to prepare regular metal-organic networks with long range ordering for three molecular linkers. In all cases the networks were prepared with the Dy and Er and presented the same structure for the two metals. Additionally, one of the molecules resulted in an organometallic architecture with a metallocenes structure.
The electronic and magnetic properties of the regular metal-organic and organometallic systems prepared were investigated using scanning tunneling spectroscopy (STS), x-ray absorption spectroscopy (XAS), x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD). It was observed that, even if the structure is the same for Dy and Er, there is a change in theelectronic and magnetic properties with the exchange of the metallic atom between Dy and Er. When exchanging the metallic center there is a reorientation of the easy axis of magnetization and a change in the intensity of the magnetic anisotropy. These results indicate that it is possible to tailor the magnetic properties of lanthanides elements on surfaces by the coordination with molecular linkers.
The results were presented in one national and four international conferences. Three scientific articles have already been published in peer reviewed journals in open access format. The articles were advertised in press-releases in institutional websites and social medias.
The electronic and magnetic properties of the regular metal-organic and organometallic systems prepared were investigated using scanning tunneling spectroscopy (STS), x-ray absorption spectroscopy (XAS), x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD). It was observed that, even if the structure is the same for Dy and Er, there is a change in theelectronic and magnetic properties with the exchange of the metallic atom between Dy and Er. When exchanging the metallic center there is a reorientation of the easy axis of magnetization and a change in the intensity of the magnetic anisotropy. These results indicate that it is possible to tailor the magnetic properties of lanthanides elements on surfaces by the coordination with molecular linkers.
The results were presented in one national and four international conferences. Three scientific articles have already been published in peer reviewed journals in open access format. The articles were advertised in press-releases in institutional websites and social medias.
The project explored fields in the frontiers of knowledge providing an insight of fundamental aspects of physics and coordination chemistry on surfaces in an interdisciplinary study. It contributed to an advance in the understanding of the properties of nanoscale lanthanides architectures. The 4-Mag project unveiled strategies for the design and characterization of lanthanide metal-organic networks. Moreover, it paved new path ways for the engenering of the electronic and magnetic properties at nanoscale.