Molecular Thin Films: A New Type of Magnetic Switch

Abstract

The design and fabrication of materials that exhibit both semiconducting and magnetic properties for spintronics and quantum computing has proven difficult. Important starting points are high-purity thin films as well as fundamental theoretical understanding of the magnetism. Here we show that small molecules have great potential in this area, due to ease of insertion of localised spins in organic frameworks and both chemical and structural purity. In particular, we demonstrate that archetypal molecular semiconductors, namely the metal phthalocyanines (Pc), can be readily fabricated as thin film quantum antiferromagnets, important precursors to a solid state quantum computer. Their magnetic state can be switched via fabrication steps which modify the film structure, offering practical routes into information processing. Theoretical calculations show that a new mechanism, which is the molecular analogue of the interactions between magnetic ions in metals, is responsible for the magnetic states. Our combination of theory and experiments opens the field of organic thin film magnetic engineering

Molecular Order in Buried Layers of TbPc2 Single‐Molecule Magnets Detected by Torque Magnetometry

“…[1] Similarly, for the development of new molecule-based devices like molecular spin-valves, molecular orientation needs to be deeply investigated and controlled. Some molecular magnetic materials may exhibit structural polymorphs which differ dramatically by the magnitude [2] or the sign [3] of the exchange coupling interaction. Single-Molecule Magnets are strongly sensitive to structural order [4] and a different orientation of the magnetic anisotropy can allow a different coupling with a functional substrate thus altering the magnetism of the hybrid molecular system in addition to its transport properties.…”

Communication: Influence of graphene interlayers on the interaction between cobalt phthalocyanine and Ni(111)

“…A main reason for the growing interest in transition metal phthalocyanines (TMPc) is their possible application in optoelectronic devices such as organic field effect transistors (OFETs), [1][2][3] organic light emitting devices (OLEDs), [4][5][6] organic photovoltaics (OPV), 4,7 and spintronic devices. [8][9][10] Increasing experimental and theoretical research efforts are devoted to the understanding of the electronic structure of this class of materials and in particular to related interfaces. [11][12][13] The performance of devices based on these materials highly depends on the behavior of the organic molecules at the interfaces with metals.…”

Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine

“…These functionals listed in Fig.1 and Fig.2 have predicted a ferromagnetic interaction except for HSE06 giving an anti-ferromagnetic one. However, these calculated exchange interactions is much larger than the nearest-neighbouring exchange interaction in CuPc crystal (typically ∼ 0.1 meV) [2,4] and the hyperfine interaction on CuPc (typically ∼ 10 −5 meV) [11].…”

“…They can have very long spin-lattice relaxation times [11], which may pave the way towards robust electron-spin qubit. Moreover, as organic semiconductors, due to their plasticity, they can be prepared in different forms such as bulk crystalline, thin films [2,8], and nanowires [3]. In conjugation with their magnetic tunability realised by the state-of-the-art molecular growth techniques [2,8], these advanced materials properties are highly promising in the applications including quantum information processing (QIP) [11] and organic spintronics [12].…”