Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires

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Abstract

Whenever a nanosystem such as an adatom, a cluster or a nanowire spontaneously magnetizes, a crucial parameter is its magnetic anisotropy, the intrinsic preference of magnetization to lie along an easy axis1. Anisotropy is important in nanosystems because it helps reduce the magnitude of thermal (superparamagnetic) fluctuations, it can modify the flow of current, and it can induce new phenomena, such as the quantum tunnelling of magnetization2. We discuss here, on the basis of density functional calculations, the novel and unconventional feature of colossal magnetic anisotropy—the strict impossibility of magnetization to rotate from the parallel to the orthogonal direction—which, owing to a quantum mechanical selection rule, the recently predicted Pt nanowire magnetism should exhibit. Model calculations suggest that the colossal magnetic anisotropy of a Pt chain should persist after weak adsorption on an inert substrate or surface step.

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Figure 1: Magnetic moments and energy gains versus interatomic spacing d in a suspended monatomic Pt nanowire.
Figure 2: Monatomic Pt nanowire at zero-strain interatomic spacing d0 = 2.35 Å.
Figure 3: The onset of magnetism in a suspended Pt nanowire.
Figure 4: Pt nanowire (at equilibrium spacing) deposited symmetrically on a surface step.

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Acknowledgements

Work in SISSA was sponsored by PRIN Cofin 2006022847, as well as by INFM/CNR ‘Iniziativa trasversale calcolo parallelo’. R.W. is a member of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina) and gratefully acknowledges fruitful discussions with J. Guevara. Support from grants PICT No. 03-13996 (ANPCyT-Argentina) and PIP No. 6135 (CONICET) is also acknowledged. A.D. acknowledges financial support from VR, the European Commission and SSF.

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Correspondence to E. Tosatti.

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Smogunov, A., Dal Corso, A., Delin, A. et al. Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires. Nature Nanotech 3, 22–25 (2008) doi:10.1038/nnano.2007.419

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