Berlin 2012 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 9: Poster I - Biomagnetism, FePt Nanoparticles, Magnetic Particles/Clusters, Magnetic Materials, Magnetic Semiconductors, Half-metals/Oxides, Multiferroics, Topological Insulators, Spin structures/Phase transitions, Electron theory/Computational micromagnetics, Magnetic coupling phenomena/Exchange bias, Spin-dependent transport, Spin injection/spin currents, Magnetization/Demagnetization dynamics, Magnetic measurement techniques

DF 9.11: Poster

Dienstag, 27. März 2012, 12:15–15:15, Poster A

Spin-fluctuation energies in 3d transition-metal clusters deposited on Pt (111) — •Sergej Riemer¹, Gustavo Pastor², Jesus Dorantes-Dávila³, and Raul Garibay-Alonso⁴ — ¹Universität Kassel, Germany — ²Universität Kassel, Germany — ³UASLP, San Luis Potosí, Mexico — ⁴Universidad Autónoma de Coahuila, Mexico

A functional-integral theory of itinerant magnetism is applied to transition-metal clusters deposited on Pt (111). The low temperature limit of the local spin-fluctuation energies Δ F_l(ξ) at different atoms l is determined as a function of the exchange field ξ by using a real-space recursive expansion of the local Green’s functions. The size, structural, and local-environment dependence of Δ F_l(ξ) is calculated for representative examples of Fe_N, Co_N and Ni_N with N ≤ 13 atoms. The interplay between fluctuations of the module and of the relative orientation of the local magnetic moments is analyzed. Comparison between free and deposited clusters having the same structure and interatomic distances reveals remarkable changes in the spin-excitation spectrum of the clusters as a result of the hybridizations with the metallic support. For instance, in the case of small Fe clusters on Pt (111) one observes that the spin-flip energies are reduced by more than an order of magnitude as a consequence of deposition. A similar important reduction of the Curie temperature is expected. This contrasts with the results for the ground-state magnetic moments and magnetic order, which are essentially the same in the free and deposited configurations.