James Broadhurst, Giuseppe Mallia, Nicholas Harrison
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引用次数: 0
摘要
自旋电子学的一个长期目标是产生在室温下具有稳定磁有序性的有机自旋半导体材料。为此,过渡金属酞菁类化合物在实现这一目标方面大有可为。其中,α-相钴 (II) 酞菁(α-CoPc)表现出很强的反铁磁交换相互作用,可产生高达 ∼100 K 的长程有序。本报告以哈伯德哈密顿为基础,提出了一种简单的机制,阐明了 α-CoPc 中的交换耦合。该机制提供了增加磁耦合的规定,并由此提出了用铑取代中心钴离子将导致耦合强度显著增加的建议。这种交换相互作用的强度已通过破对称混合交换密度泛函理论进行了评估,结果表明,新型铑 (II) 酞菁体系确实会表现出明显更强的磁有序性。因此,这项研究确定了 α-CoPc 的耦合机制主要归因于动力学交换,解释了之前报道的相对于其第一排过渡金属对应物的强耦合,并表明铑 (II) 酞菁有可能在室温下表现出稳定的磁有序性。
A prediction of high temperature magnetic coupling in transition metal phthalocyanines.
In spintronics, a perennial goal has been the generation of organic spin-bearing semiconductor materials with magnetic ordering stable at room temperature. To this end, the class of transition metal phthalocyanines has shown much promise in fulfilling this ambition. In particular, alpha-phase cobalt (II) phthalocyanine (α-CoPc) exhibits strong antiferromagnetic exchange interactions producing a long range order up to ∼100 K. However, the underlying mechanism by which this magnetic interaction proceeds is not well understood. In this report, a simple mechanism has been proposed based on the Hubbard Hamiltonian, which elucidates the exchange coupling in α-CoPc. The mechanism provides stipulations for increasing the magnetic coupling, and this directs to a proposal that substitution of the central cobalt ion for rhodium will lead to a significant increase in coupling strength. The strength of this exchange interaction has been evaluated using broken symmetry hybrid exchange density functional theory and indicates that the novel rhodium (II) phthalocyanine system is indeed predicted to exhibit significantly stronger magnetic ordering. This study, therefore, identifies the coupling mechanism in α-CoPc as primarily attributable to kinetic exchange, explains its previously reported strong coupling relative to its first-row transition metal counterparts, and suggests that rhodium (II) phthalocyanine is likely to exhibit stable magnetic ordering at room temperature.
期刊介绍:
The Journal of Chemical Physics publishes quantitative and rigorous science of long-lasting value in methods and applications of chemical physics. The Journal also publishes brief Communications of significant new findings, Perspectives on the latest advances in the field, and Special Topic issues. The Journal focuses on innovative research in experimental and theoretical areas of chemical physics, including spectroscopy, dynamics, kinetics, statistical mechanics, and quantum mechanics. In addition, topical areas such as polymers, soft matter, materials, surfaces/interfaces, and systems of biological relevance are of increasing importance.
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