Magnetic behaviour of TbPc2 single-molecule magnets chemically grafted on silicon surface (original) (raw)
Related papers
Nano Letters, 2008
The electronic structure of isolated bis(phthalocyaninato) terbium(III) molecules, a novel single-molecular-magnet (SMM), supported on the Cu(111) surface has been characterized by density functional theory and scanning tunneling spectroscopy. These studies reveal that the interaction with the metal surface preserves both the molecular structure and the large spin magnetic moment of the metal center. The 4f electron states are not perturbed by the adsorption while a strong molecular/metal interaction can induce the suppression of the minor spin contribution delocalized over the molecular ligands. The calculations show that the inherent spin magnetic moment of the molecule is only weakly affected by the interaction with the surface and suggest that the SMM character might be preserved.
Coupling Single Molecule Magnets to Ferromagnetic Substrates
Physical Review Letters, 2011
We investigate the interaction of TbPc2 single molecule magnets (SMMs) with ferromagnetic Ni substrates. Using element-resolved x-ray magnetic circular dichroism, we show that TbPc2 couples antiferromagnetically to Ni films through ligand-mediated superexchange. This coupling is strongly anisotropic and can be manipulated by doping the interface with electron acceptor or donor atoms. We observe that the relative orientation of the substrate and molecule anisotropy axes critically affects the SMM magnetic behavior. TbPc2 complexes deposited on perpendicularly magnetized Ni films exhibit enhanced magnetic remanence compared to SMMs in the bulk. Contrary to paramagnetic molecules pinned to a ferromagnetic support layer, we find that TbPc2 can be magnetized parallel or antiparallel to the substrate, opening the possibility to exploit SMMs in spin valve devices.
Nanoscale, 2018
The single molecule magnet (SMM) bis(phthalocyaninato)terbium(iii) (TbPc2) has received significant and increasing attention as an exemplar system for realizing molecule-based spin electronics. Attaining higher nuclearity via multi-decker TbPc systems has remained an outstanding challenge, as known examples of Tb2Pc3 systems are only those containing Pc rings with substituents (e.g. alkyl, alkoxyl). Here we report on the spontaneous formation of Tb2Pc3 species from TbPc2 precursors via sublimation in ultrahigh vacuum (UHV) onto an Ag(111) surface. The presence of Tb2Pc3 molecules on the surface are inspected using scanning probe microscopy with submolecular resolution supported by density functional theory (DFT) calculations and additional chemical analysis. We observe the selective presence of a Kondo resonance (30 K) in the Tb2Pc3 species, that we attribute to differences in the orientation of the internal molecular ligands. Formation of triple-decker complexes offers new possibil...
Exchange Biasing Single Molecule Magnets: Coupling of TbPc 2 to Antiferromagnetic Layers
Nano Letters, 2012
We investigate the possibility to induce exchange bias between single molecule magnets (SMM) and metallic or oxide antiferromagnetic substrates. Elementresolved X-ray magnetic circular dichroism measurements reveal, respectively, the presence and absence of unidirectional exchange anisotropy for TbPc 2 SMM deposited on antiferromagnetic Mn and CoO layers. TbPc 2 deposited on Mn thin films present magnetic hysteresis and a negative horizontal shift of the Tb magnetization loop after field cooling, consistent with the observation of pinned spins in the Mn layer coupled parallel to the Tb magnetic moment. Conversely, molecules deposited on CoO substrates present paramagnetic magnetization loops with no indication of exchange bias. These experiments demonstrate the ability of SMM to polarize the pinned uncompensated spins of an antiferromagnet during field-cooling and realize metal−organic exchange-biased heterostructures using antiferromagnetic pinning layers.
X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices
Advanced Materials, 2009
The encoding of magnetic information at the molecular level finds in Single Molecule Magnets (SMM) a most promising avenue. SMM are composed of discrete metal-ion clusters which assemble into molecular crystals and offer unparalleled chemical flexibility and processability among soft magnetic materials. Their ground state has a large spin value and an easy-axis magnetic anisotropy, so that at low temperature the reversal of the molecular magnetic moment is subject to an energy barrier which can be overcome either via thermal activation or by a quantumtunneling mechanism. Each molecule in the crystal thus behaves as a nanometer-sized magnet, displaying hysteresis and fascinating quantum effects. Applications of SMM in ultrahigh-density information storage and spintronics are foreseen, which entail SMM organized into addressable layers at surfaces or incorporated into metal-molecule-metal junctions. However, fundamental aspects related to the magnetic behavior of SMM in these environments have not yet been fully explored. In fact, the spin dynamics of SMM is exceedingly sensitive to structural deformations, intermolecular interactions, and to other environmental effects, which are expected to be different for SMM hosted in a crystalline lattice, assembled into an addressable layer or incorporated in a metal-molecule-metal junction. Recently we have reported a magneto-optical investigation on the archetypal SMM, the mixed-valence Mn 12 complex, in different environments showing the disappearance of magnetic hysteresis when the clusters are organized as a SAM on gold. Further studies are necessary to assess if the slow magnetization dynamics that characterizes SMM behavior is compatible with the surface environment. With this goal in mind we have used X-ray magnetic circular dichroism, XMCD, at sub-Kelvin temperatures to investigate the surface magnetic properties of thin films made of two different SMM. We show here that SMM behavior is indeed observable for the first monolayer(s) but, surprisingly, not in the case of the widely investigated Mn 12 clusters.
Journal of the American Chemical Society, 2018
Herein we report the synthesis and characterization of a dinuclear Tb single-molecule magnet (SMM) with two [TbPc] units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the Tb ions and the two π radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc] and the axially symmetric dinuclear Tb phthalocyaninato triple-decker complex (Tb(obPc)). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc unit is P, the probability of QTM simultaneously occurring in 1 is P, meaning ...
Inducing Magnetism in Pure Organic Molecules by Single Magnetic Atom Doping
Physical Review Letters, 2014
We report on in situ chemical reactions between an organic trimesic acid (TMA) ligand and a Co atom center. By varying the substrate temperature, we are able to explore the Co-TMA interactions and create novel magnetic complexes that preserve the chemical structure of the ligands. Using scanning tunneling microscopy and spectroscopy combined with density functional theory calculations, we elucidate the structure and the properties of the newly synthesized complex at atomic or molecular size level. Hybridization between the atomic orbitals of the Co and the π orbitals of the ligand results in a delocalized spin distribution onto the TMA. The here demonstrated possibility to conveniently magnetize such versatile molecules opens up new potential applications for TMAs in molecular spintronics.