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(i) Multiplet calculations for TDA+Er; (ii) Point charges for multiplet calculations for TDA+Er; (iii) STM images; (iv) STS data; (v) XAS, XMCD and XLD data for TDA+Er

Multi-metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are of interest for the development of multifunctional materials, however examples with more than three RE cations are rare and obstructed by compositional segregation during synthesis. Herein, this work demonstrates the synthesis of a multi-metallic MTV RE MOF incorporating two, four, six, or eight different RE ions with different sizes and in nearly equimolar amounts and no compositional segregation. The MOFs are formed by a combination of RE cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) and a 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane (mCB-L) linker. The steric bulkiness and acidity of mCB-L is crucial for the incorporation of different size RE ions into the MOF structure. Demonstration of the incorporation of all RE cations is performed via compositional and structural characterization. The more complex MTV MOF, including all eight RE ions (mCB-8RE), are also characterized using optical, thermal, and magnetic techniques. Element-selective X-ray absorption spectroscopy and X-ray Magnetic Circular Dichroism measurements allow us to characterize spectroscopically each of the eight RE ions and determine their magnetic moments. This work paves the way for the investigation of MTV MOFs with the possibility to combine RE ions à la carte for diverse applications.

The coordination of lanthanides atoms in two-dimensional surface-confined metal-organic networks is a promising path to achieve an ordered array of single atom magnets. These networks are highly versatile with plenty of combinations of molecular linkers and metallic atoms. Notably, with an appropriate choice of molecules and lanthanide atoms it should be feasible to tailor the orientation and intensity of the magnetic anisotropy. However, up to now only tilted and almost in-plane easy axis of magnetizations were reported in lanthanide-based architectures. Here we introduce an Er-directed two-dimensional metallosupramolecular network on Cu(111) featuring strong out-of-plane magnetic anisotropy. Our results will contribute to pave avenues for the use of lanthanides in potential applications in nanomagnetism and spintronics.

Van der Waals (vdW) heterostructures combining layered ferromagnets and other 2D crystals are promising building blocks for the realization of ultracompact devices with integrated magnetic, electronic, and optical functionalities. Their implementation in various technologies depends strongly on the development of a bottom-up scalable synthesis approach allowing for realizing highly uniform heterostructures with well-defined interfaces between different 2D-layered materials. It is also required that each material component of the heterostructure remains functional, which ideally includes ferromagnetic order above room temperature for 2D ferromagnets. Here, it is demonstrated that the large-area growth of Fe5−xGeTe2/graphene heterostructures is achieved by vdW epitaxy of Fe5−xGeTe2 on epitaxial graphene. Structural characterization confirms the realization of a continuous vdW heterostructure film with a sharp interface between Fe5−xGeTe2 and graphene. Magnetic and transport studies reveal that the ferromagnetic order persists well above 300 K with a perpendicular magnetic anisotropy. In addition, epitaxial graphene on SiC(0001) continues to exhibit a high electronic quality. These results represent an important advance beyond nonscalable flake exfoliation and stacking methods, thus marking a crucial step toward the implementation of ferromagnetic 2D materials in practical applications.

Antiferromagnetic spintronics is a rapidly emerging field with the potential to revolutionize the way we store and process information. One of the key challenges in this field is the development of novel two-dimensional antiferromagnetic materials. In this paper, we report the first on-surface synthesis of a Co-directed metal-organic network in which the Co atoms are strongly antiferromagnetically coupled, while featuring a perpendicular magnetic anisotropy. This material is a promising candidate for future antiferromagnetic spintronic devices, as it combines the advantages of twodimensionality and metal-organic chemistry with strong antiferromagnetic order and perpendicular magnetic anisotropy.

(i) Multiplet calculations for TDA+Dy, TPA+Dy, and antiprism+Dy; (ii) Point charges for multiplet calculations for TDA+Dy and TPA+Dy; (iii) STM images for TDA+Dy and TPA+D; (iv) STS data for TDA+Dy; (v) XAS, XMCD and XNLD data for TDA+Dy, TPA+Dy and Dy clusters

(i) Multiplet calculations for DPBP+Dy and DPBP+Er; (ii) Point charges for multiplet calculations for DPBP+Dy and DPBP+Er; (iii) STM images for DPBP+Dy and DPBP+Er; (iv) STS data for DPBP+Dy and DPBP+Er; (v) XAS, XMCD and XLD data for DPBP+Dy and DPBP+Er

[EN] The design of lanthanide multinuclear networks is an emerging field of research due to the potential of such materials for nanomagnetism, spintronics, and quantum information. Therefore, controlling their electronic and magnetic properties is of paramount importance to tailor the envisioned functionalities. In this work, a multidisciplinary study is presented combining scanning tunneling microscopy, scanning tunneling spectroscopy, X-ray absorption spectroscopy, X-ray linear dichroism, X-ray magnetic circular dichroism, density functional theory, and multiplet calculations, about the supramolecular assembly, electronic and magnetic properties of periodic dinuclear 2D networks based on lanthanide-pyridyl interactions on Au(111). Er- and Dy-directed assemblies feature identical structural architectures stabilized by metal–organic coordination. Notably, despite exhibiting the same +3 oxidation state, there is a shift of the energy level alignment of the unoccupied molecular orbitals between Er- and Dy-directed networks. In addition, there is a reorientation of the easy axis of magnetization and an increment of the magnetic anisotropy when the metallic center is changed from Er to Dy. Thus, the results show that it is feasible to tune the energy level alignment and magnetic anisotropy of a lanthanide-based metal-organic architecture by metal exchange, while preserving the network design.

Nanometer-thick epitaxial Co films intercalated between graphene (Gr) and a heavy metal (HM) substrate are promising systems for the development of spin-orbitronic devices due to their large perpendicular magnetic anisotropy (PMA). A combination of theoretical modeling and experiments reveals the origin of the PMA and explains its behavior as a function of the Co thickness. High quality epitaxial Gr/Co-n/HM(111) (HM = Pt,Ir) heterostructures are grown by intercalation below graphene, which acts as a surfactant that kinetically stabilizes the pseudomorphic growth of highly perfect Co face-centered tetragonal (fct) films, with a reduced number of stacking faults as the only structural defect observable by high-resolution scanning transmission electron microscopy (STEM). Magneto-optic Kerr effect (MOKE) measurements show that such heterostructures present PMA up to large Co critical thicknesses of about 4 nm (20 ML) and 2 nm (10 ML) for Pt and Ir substrates, respectively. X-ray magnetic circular dichroism (XMCD) measurements show an inverse power law of the anisotropy of the orbital moment with Co thickness, reflecting its interfacial nature, that changes sign at about the same critical values. First principles calculations show that, regardless of the presence of graphene, ideal Co fct films on HM buffers do not sustain PMAs beyond around 6 mLs due to the in-plane contribution of the inner bulk-like Co layers. The large experimental critical thicknesses sustaining PMA can only be retrieved by the inclusion of structural defects that promote a local hcp stacking such as twin boundaries or stacking faults. Remarkably, a layer resolved analysis of the orbital momentum anisotropy reproduces its interfacial nature, and reveals that the Gr/Co interface contribution is comparable to that of the Co/Pt(Ir).

Taming the magnetic anisotropy of lanthanides through coordination environments is crucial to take advantage of the lanthanides properties in thermally robust nanomaterials. In this work, the electronic and magnetic properties of Dy-carboxylate metal–organic networks on Cu(111) based on an eightfold coordination between Dy and ditopic linkers are inspected. This surface science study based on scanning probe microscopy and X-ray magnetic circular dichroism, complemented with density functional theory and multiplet calculations, reveals that the magnetic anisotropy landscape of the system is complex. Surface-supported metal–organic coordination is able to induce a change in the orientation of the easy magnetization axis of the Dy coordinative centers as compared to isolated Dy atoms and Dy clusters, and significantly increases the magnetic anisotropy. Surprisingly, Dy atoms coordinated in the metallosupramolecular networks display a nearly in-plane easy magnetization axis despite the out-of-plane symmetry axis of the coordinative molecular lattice. Multiplet calculations highlight the decisive role of the metal–organic coordination, revealing that the tilted orientation is the result of a very delicate balance between the interaction of Dy with O atoms and the precise geometry of the crystal field. This study opens new avenues to tailor the magnetic anisotropy and magnetic moments of lanthanide elements on surfaces.

We report a comprehensive study on the magnetic ground state of La1.5Ca0.5CoO4 combining single crystal neutron diffraction and resonant magnetic x-ray scattering at the CoL2,3 edges. Three single-crystal samples obtained from the same boule were investigated exhibiting magnetic phase transitions from a high-temperature paramagnetic phase to an antiferromagnetic phase at TN≈52K. Single crystal neutron diffraction reveals that the crystal structure at room temperature shows an orthorhombic A-centered lattice but with a and b axes almost equal in length. The structural phase transition (charge-ordering-like) from the parent tetragonal cell takes place above 523 K into the space group A2mm where two nonequivalent compressed and expanded CoO6 octahedra are ordered showing a checkerboard pattern in the ab plane. The charge segregation between the nonequivalent Co sites is about 0.4(1) electrons. Resonant magnetic x-ray reflections indexed as (1/4,1/4,0)t, (1/4,1/4,1)t, and (1/4,1/4,1/2)t in the parent tetragonal cell were observed at low temperature at the CoL2,3-edge energy range. The resonant spectral shape, with a noticeable absence of any resonant enhancement at the CoL2 edge, indicates that only Co2+-like ions participate in the magnetic ordering. The polarization analysis discloses that the orientation of Co magnetic moments is the same for the three magnetic orders and they are long-range ordered along the diagonal in the ab plane of the parent tetragonal cell with a slight tilt in the c axis. Despite the onset temperatures for the three resonant magnetic reflections being the same, ≈55K, different thermal behavior is observed between (1/4,1/4,1/2)t and (1/4,1/4,L)t (L=integer) reflections whose intensities maximize at different temperatures, suggesting the coexistence of two magnetic arrangements. Moreover, the intensity of the (1/4,1/4,1/2)t magnetic reflection is at least ten times larger than that of the (1/4,1/4,L) t (L=integer) ones. On the other hand\, neut

Scalable fabrication of magnetic 2D materials and heterostructures constitutes a crucial step for scaling down current spintronic devices and the development of novel spintronic applications. Here, we report on van der Waals (vdW) epitaxy of the layered magnetic metal Fe3GeTe2 (FGT) - a 2D crystal with highly tunable properties and a high prospect for room temperature ferromagnetism (FM) - directly on graphene by employing molecular beam epitaxy. Morphological and structural characterization confirmed the realization of large-area, continuous FGT/graphene heterostructure films with stable interfaces and good crystalline quality. Furthermore, magneto-transport and x-ray magnetic circular dichroism investigations confirmed a robust out-of-plane FM in the layers, comparable to state-of-the-art exfoliated flakes from bulk crystals. These results are highly relevant for further research on wafer-scale growth of vdW heterostructures combining FGT with other layered crystals such as transition metal dichalcogenides for the realization of multifunctional, atomically thin devices.

Nanometer-thick epitaxial Co films intercalated between graphene (Gr) and a heavy metal (HM) substrate are promising systems for the development of spin–orbitronic devices due to their large perpendicular magnetic anisotropy (PMA). A combination of theoretical modeling and experiments reveals the origin of the PMA and explains its behavior as a function of the Co thickness. High quality epitaxial Gr/Con/HM(111) (HM = Pt,Ir) heterostructures are grown by intercalation below graphene, which acts as a surfactant that kinetically stabilizes the pseudomorphic growth of highly perfect Co face-centered tetragonal (fct) films, with a reduced number of stacking faults as the only structural defect observable by high-resolution scanning transmission electron microscopy (STEM). Magneto-optic Kerr effect (MOKE) measurements show that such heterostructures present PMA up to large Co critical thicknesses of about 4 nm (20 ML) and 2 nm (10 ML) for Pt and Ir substrates, respectively. X-ray magnetic circular dichroism (XMCD) measurements show an inverse power law of the anisotropy of the orbital moment with Co thickness, reflecting its interfacial nature, that changes sign at about the same critical values. First principles calculations show that, regardless of the presence of graphene, ideal Co fct films on HM buffers do not sustain PMAs beyond around 6 mLs due to the in-plane contribution of the inner bulk-like Co layers. The large experimental critical thicknesses sustaining PMA can only be retrieved by the inclusion of structural defects that promote a local hcp stacking such as twin boundaries or stacking faults. Remarkably, a layer resolved analysis of the orbital momentum anisotropy reproduces its interfacial nature, and reveals that the Gr/Co interface contribution is comparable to that of the Co/Pt(Ir).