When Molecular Dimerization Induces Magnetic Bi‐Stability at the Metal–Organic Interface

Abstract 2D metal–organic frameworks have been recently proposed as a flexible platform for realizing new functional materials including quantum phases. Here, we present a method to create metal‐organic dimer complexes by on‐surface assembly on a metal substrate using low‐temperature scanning tunneling microscopy (STM) and spectroscopy (STS). We demonstrate that a dimer of Mn‐Phthalocyanine (MnPc)2 on a Ag(111) surface can be switched between two stable configurations upon a small conformational change controlled by STM manipulation. By means of density‐functional theory calculations, it is found that the two conformations correspond to an antiferromagnetic (AFM) and a ferromagnetic (FM) state respectively. Directly coordinated Mn atoms of the dimer lead to an AFM‐coupling whereas indirectly coordinated (shifted) Mn atoms lead to a FM‐coupling. Rarely seen in a molecular‐dimers with transition‐metal atoms, the FM‐AFM‐FM transition is thus readily on‐surface accessible. Furthermore, the two configurations of the switch are easily identified by their Kondo states, opening interesting routes in terms of both, writing (FM versus AFM states) and reading. These results pave the experimental route toward dimer‐based materials with complex magnetic structures of potential interest for application in spintronics, logics and computing

Fluorinated Phthalocyanine Molecules on Ferromagnetic Cobalt: A Highly Polarized Spinterface

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Quantum advantage in a spintronic engine with coherently coupled ultrafast strokes using molecular superexchange

Recent theory and experiments have showcased how to harness quantum mechanics to assemble heat/information engines with efficiencies that surpass the classical Carnot limit. So far, implementing work-producing quantum resources has required atomic engines driven by external laser and microwave energy sources We propose a spin electronic implementation that operates autonomously. Our concept heuristically deploys several known quantum resources upon placing a quantum-entangled chain of spin qubits formed by the Co centers of phthalocyanine (Pc) molecules between electron-spin selecting Fe/C60 interfaces. Density functional calculations reveal that transport fluctuation strokes across the interfaces can stabilize spin coherence on the Co paramagnetic centers, which host spin swap engine strokes. Across solid-state vertical molecular nanojunctions, we measure large enduring dc current generation, sizeable output power above room temperature, and two quantum thermodynamical signatures. The Fe/C60 interface's record 89% spin polarization also enables a spintronic feedback and control over the flow and direction of charge current. Beyond these first results, further research into spintronic quantum engines, and retooling the spintronic-based information technology chain7, could help accelerate the transition to clean energy.Comment:

Encoding Information on the Excited State of a Molecular Spin Chain

International audienceThe quantum states of nano-objects can drive electrical transport properties across lateral and local-probe junctions. This raises the prospect, in a solid-state device, of electrically encoding information at the quantum level using spinflip excitations between electron spins. However, this electronic state has no defined magnetic orientation and is short-lived. Using a novel vertical nanojunction process, these limitations are overcome and this steady-state capability is experimentally demonstrated in solid-state spintronic devices. The excited quantum state of a spin chain formed by Co phthalocyanine molecules coupled to a ferromagnetic electrode constitutes a distinct magnetic unit endowed with a coercive field. This generates a specific steady-state magnetoresistance trace that is tied to the spin-flip conductance channel, and is opposite in sign to the ground state magnetoresistance term, as expected from spin excitation transition rules. The experimental 5.9 meV thermal energy barrier between the ground and excited spin states is confirmed by density functional theory, in line with macrospin phenomenological modeling of magnetotransport results. This low-voltage control over a spin chain's quantum state and spintronic contribution lay a path for transmitting spin wave-encoded information across molecular layers in devices. It should also stimulate quantum prospects for the antiferromagnetic spintronics and oxides electronics communities