Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 39: Magnetism in Thin Films: Interaction Phenomena and Heterostructures

DS 39.3: Talk

Friday, February 29, 2008, 11:15–11:30, H 2032

FeZr-based multilayers – a frustrated XY system? — •Andreas Liebig¹, Panagiotis Korelis¹, Gabriella Andersson¹, Björgvin Hjörvarsson¹, Hans Lidbaum², and Klaus Leifer² — ¹Dep. of Physics, Uppsala University, Uppsala, Sweden — ²Dep. of Engineering Sciences, Uppsala University, Uppsala, Sweden

Anisotropy and frustration terms can lead to a reentrant spin-glass state at low temperatures in the amorphous ferromagnet Fe₉₀Zr₁₀.

Here, we present a study of Fe₉₀Zr₁₀/Al₇₀Zr₃₀ amorphous multilayers, using MOKE and a SQUID magnetometry. The structural quality was verified using X-ray reflectivity as well as HR-TEM and the chemical composition was determined by RBS.

Interlayer exchange coupling across the amorphous Al₇₀Zr₃₀ layer is weak and the ordering temperature is therefore almost exclusively dominated by the thickness of the Fe₉₀Zr₁₀ layers. Multilayers with Fe₉₀Zr₁₀ layers in the nm range are found to have extraordinarily low remnant and coercive fields – in fact, so low that the definition of a magnetic transition temperature becomes difficult. The magnetization of the layers collapses, with exceedingly high susceptibility above the apparent ordering temperature.

A conceptual model of the transition will be given, involving the competition between the local anisotropy and the exchange coupling. The results can have far reaching consequences for the understanding of the interplay between finiteness and ordering. For example, the use of nearest neighbour interaction is found to be insufficient for describing the observations.