Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.80: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Thermal Switching Behavior of Superparamagnetic Nanoislands: SP-STM on Fe/W(110) — •Gabriela Herzog¹, Stefan Krause¹, Luis Berbil-Bautista^1,2, Elena Vedmedenko¹, Matthias Bode¹, and Roland Wiesendanger¹ — ¹Institute of Applied Physics, University of Hamburg, Germany — ²Department of Physics, University of California at Berkeley, USA

Recently it has been shown that spin-polarized tunneling microscopy (SP-STM) can be applied to investigate the dynamic thermal magnetization switching processes of individual superparamagnetic nanoislands in real time [1]. While the experiments of Ref. [1] were performed only for a very limited temperature range, we have now used a home-built variable-temperature STM for detailed temperature-dependent investigations to examine the so-called Néel-Brown law, which predicts an Arrhenius-like behavior of coherently switching nanomagnets.

Our sample consists of in-plane magnetized uniaxial Fe monolayer islands on W(110). For islands with an area of approximately 20 nm² we find a blocking temperature of about 45 K. The high stability of our experimental setup allows the observation of the same islands over a temperature range between 40 K and 50 K, causing a variation of the switching rate by three orders of magnitude. The experimental data as well as Monte-Carlo simulations reveal that within this temperature range a crossover from coherent rotation to the nucleation of domain walls occurs.

[1] M. Bode et al., Phys. Rev. Lett. 92, 067201 (2004).