Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 60: SC \& MLT: Cryodetectors

TT 60.3: Hauptvortrag

Freitag, 18. März 2011, 11:00–11:30, HSZ 301

Engineering Atomic-Scale Spin Systems — •Sebastian Loth — IBM Research - Almaden, San Jose, CA

When magnetic structures shrink to a point where they consist of only a few atoms, their continuously variable magnetization transforms into a spin with quantized states. Their dynamical behavior is determined by the energetic distribution of these states. We demonstrate that low temperature scanning tunneling microscopy can access both the energetic and dynamical properties of electron spins in transition metal atoms that were placed on a Cu₂N overlayer on Cu(100).

Inelastic electron tunneling spectroscopy measures the transition energies of the atomic spins. Fe atoms experience large easy-axis anisotropy leading to a potentially bistable configuration, whereas Mn atoms in high magnetic field form a uniform ladder of spin states that is inherently unstable. The STM gains access to the corresponding dynamical evolution by all-electronic pump-probe spectroscopy. We measure the spin relaxation time of individual atoms or nanostructures with nanosecond precision and find that placing Cu atoms in decreasing distances to Fe atoms successively boosts the Fe atom’s magnetic anisotropy energy and increases the spin relaxation time beyond 200 ns.

For potential spintronics applications, these experiments demonstrate the ability to manipulate the energetic structure of individual atomic spins and to directly monitor the resulting effect on the spin dynamics.