Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 38: Magnetic Materials II

MA 38.1: Vortrag

Donnerstag, 3. April 2014, 09:30–09:45, HSZ 403

Synthesis and properties of ultrathin B2 ordered FeRh films — •Ralf Witte, Richard Brand, Robert Kruk, and Horst Hahn — Karlsruhe Institute of Technology KIT, Institute for Nanotechnology, 76344 Eggenstein, Germany

The B2 ordered phase (CsCl structure) of the Fe50Rh50 alloys possess interesting magnetic properties. They are antiferromagnetically (AFM) coupled at room temperature and show a transition to a ferromagnetic phase (FM) at about 400K. This behavior has been shown in bulk material and as well in thin films. Generally, stabilization of the FM phase is associated with the Rh spin state; in the AFM phase the magnetic moment on the Rh atom is zero, while it gets polarized in the FM state. It has been calculated [1] that the FM state can be stabilized at room temperature in (freestanding, single crystalline) films with a thickness below a critically value of 9 atomic layers. This effect is attributed to the increased polarizability of the Rh atoms at the surface, which in turn stabilizes the FM state in the entire film. So far there has been no clear experimental confirmation of the theoretical results, mainly because of the difficulties in growing B2-ordered FeRh alloys in the form of an epitaxial, ultra-thin film. We present research on the synthesis and properties of FeRh thin films on different single crystalline substrates prepared by electron beam evaporation. The samples are characterized using e.g. high-resolution X-ray diffraction, atomic force microscopy, SQUID magnetometry, X-ray photo electron spectroscopy and 57Fe Mössbauer spectroscopy.

[1] S. Lounis, Phys. Rev. B 67, 094432 (2003)