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MA: Fachverband Magnetismus

MA 29: Spin Structures / Magnetic Phase Transitions

MA 29.5: Talk

Thursday, February 28, 2008, 18:45–19:00, H 1012

Antiferromagnet — ferromagnet transition in Fe islands on Cu(111) — •Timofey Balashov¹, Albert F. Takacs¹, Markus Däne², Arthur Ernst², Patrick Bruno², and Wulf Wulfhekel¹ — ¹Physikalisches Institut, Universität Karlsruhe, Wolfgang-Gaede Strasse 1, 76131 Karlsruhe, Germany — ²Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany

Fe is known for its martensitic phase transition between fcc and bcc configurations. Recently, it has been shown that 2ML Fe islands on Cu(111) show both configurations, an fcc core and a bcc outer rim [1]. We investigated the electronic structure of the Fe islands by scanning tunneling spectroscopy at 4K. By comparison to the local density of states obtained from ab-initio calculations, we were able to show that the core is antiferromagnetic while the rim of the island is ferromagnetic. Hand in hand with this phase change, Fe adopts different out of plane lattice constants as determined by topographic and spectroscopic STM investigations.

Most interestingly, we discovered that the Fe structure can be switched hysteretically between the two states by the presence of the STM tip. The transition occurs at nano Ampere currents and is also visible in topographical data, due to lattice transitions.

[1] A. Biedermann, W. Rupp, M. Schmid and P. Varga, Phys. Rev. B 73, 165418 (2006)