It is accepted that only three elements are ferromagnetic at room temperature, the transition metals iron, cobalt and nickel. The Stoner criterion explains why, for example, iron is ferromagnetic but manganese is not, even though both elements have an unfilled 3d shell and are adjacent in the periodic table: the product of the density of states with the exchange integral must be greater than unity for spontaneous ordering to emerge.1,2 Here, we demonstrate that it is possible to alter the electronic states of nonferromagnetic materials, such as diamagnetic copper and paramagnetic manganese, in 2 order to drive them ferromagnetic at room temperature. This remarkable effect is achieved via interfaces between metallic thin films and C 60 molecular layers. The emergent ferromagnetic state can exist over several layers of the metal before being quenched at large sample thicknesses by the material's bulk properties. While the induced magnetisation is easily measurable by magnetometry, low energy muon spin spectroscopy 3 provides insight into its magnetic distribution by studying the depolarisation process of low energy muons implanted in the sample. This technique indicates localized spin-ordered states at and close to the metallo-molecular interface.Density functional theory simulations suggest a mechanism based on magnetic hardening of the metal atoms due to electron transfer. 4,5 This opens a path for the exploitation of molecular coupling to design magnetic metamaterials using abundant, non-toxic elements such as organic semiconductors. Charge transfer at molecular interfaces can then be used to control spin polarisation or magnetisation, with far reaching consequences in the design of devices for electronic, power or computing applications. 6,7 Multifunctional materials with the spin degree of freedom such as multiferroics, magnetic semiconductors and molecular magnets have all aroused huge interest as potentially transformative components in quantum technologies. [8][9][10][11][12] Strategies used to bring magnetic ordering to these materials typically rely on the inclusion of magnetic transition metals, heavy elements with a large atomic moment or rare earths. In thin film structures, proximity effects and coupling at interfaces play an essential role. 13,14 This is especially the case for molecular spintronics, 15,16 where organic thin films grown on copper have demonstrated spin filtering. 17The organic magnetic coupling can propagate for long distances in systems such as nanoscale vortex-like configurations or nanoskyrmion lattices. 183We choose C 60 as a model molecule due to its structural simplicity and robustness as well as its high electron affinity. C 60 /transition metal complexes exhibit strong interfacial coupling between metal 3d z electrons and molecular π-bonded p electrons. The potential created by the mismatch of molecular and metal work functions leads to a partial filling of the interface states. [19][20][21] Other molecules with close electron affinity and the potential for 3d z /p coupling ...

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Hollow metallic nanostructures have shown potential in various applications including catalysis, drug delivery and phototherapy, owing to their large surface areas, reduced net density, and unique optical properties. In this study, novel hollow gold nanoflowers (HAuNFs) consisting of an open hollow channel in the center and multiple branches/tips on the outer surface are fabricated for the first time, via a facile one-step synthesis using an auto-degradable nanofiber as a bifunctional template. The one-dimensional (1D) nanofiber acts as both a threading template as well as a promoter of the anisotropic growth of the gold crystal, the combination of which leads to the formation of HAuNFs with a hollow channel and nanospikes. The synergy of favorable structural/surface features, including sharp edges, open cavity and high-index facets, provides our HAuNFs with excellent catalytic performance (activity and cycling stability) coupled with large single-particle SERS activity (including ∼30 times of activity in ethanol electro-oxidation and ∼40 times of single-particle SERS intensity, benchmarked against similar-sized solid gold nanospheres with smooth surfaces, as well as retaining 86.7% of the initial catalytic activity after 500 cycles in ethanol electro-oxidation). This innovative synthesis gives a nanostructure of the geometry distinct from the template and is extendable to fabricating other systems for example, hollow-channel silver nanoflowers (HAgNFs). It thus provides an insight into the design of hollow nanostructures via template methods, and offers a versatile synthetic strategy for diverse metal nanomaterials suited for a broad range of applications.

Domain walls in ferromagnetic nanowires are potential building-blocks of future technologies such as racetrack memories, in which data encoded in the domain walls are transported using spin-polarised currents. However, the development of energy-efficient devices has been hampered by the high current densities needed to initiate domain wall motion. We show here that a remarkable reduction in the critical current density can be achieved for in-plane magnetised coupled domain walls in CoFe/Ru/CoFe synthetic ferrimagnet tracks. The antiferromagnetic exchange coupling between the layers leads to simple Néel wall structures, imaged using photoemission electron and Lorentz transmission electron microscopy, with a width of only ~100 nm. The measured critical current density to set these walls in motion, detected using magnetotransport measurements, is 1.0 × 1011 Am−2, almost an order of magnitude lower than in a ferromagnetically coupled control sample. Theoretical modelling indicates that this is due to nonadiabatic driving of anisotropically coupled walls, a mechanism that can be used to design efficient domain-wall devices.

International audienceNanostructured materials often have properties widely different from bulk, imposed by quantum limits to a physical property of the material. This includes, for example, superparamagnetism and quantized conductance, but original properties such as magnetoresistance in nonmagnetic molecular structures may also emerge. In this Letter, we report on the atomic manipulation of platinum nanocontacts in order to induce magnetoresistance. Platinum is a paramagnetic 5d metal, but atomic chains of this material have been predicted to be magnetically ordered with a large anisotropy. Remarkably, we find that a gas flow stabilizes Pt atomic structures in a break junction experiment, where we observe extraordinary resistance changes over 30 000% in a temperature range up to 77 K. Simulations indicate that this behavior may stem from a previously unknown magnetically ordered, low-energy state in platinum oxide atomic chains. This is supported by measurements in Pt/ PtOx superlattices revealing the presence of a ferromagnetic moment. These properties open new paths of research for atomic scale " dirty " magnetic sensors and quantum devices