Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 14: Poster: Schichten(1-31), Spinabh.Trsp.(32-47), Exch.Bias(48-54), Spindyn.(55-64), Mikromag.(65-76), Partikel(77-88), Oflmag.(89-92), Spinelektr.(93-98), Elektr.Theo.(99-103), Mikromag+PhasÜ+Aniso.(104-122), MagnMat.(123-134), Messm+Mol-Mag.(135-139), Kondo(140-151)

MA 14.64: Poster

Dienstag, 25. März 2003, 15:15–19:15, Zelt

Electron Spin Resonance in GdBaCo₂O_5.5 — •Joachim Deisenhofer, Hans-Albrecht Krug von Nidda, Michalis Paraskevopoulos, and Alois Loidl — Experimentalphysik V, Center for Electronic Correlations and Magnetism, Institute for Physics, Augsburg University, D-86135 Augsburg, Germany

We have performed ESR experiments in GdBaCo₂O_5.5 at X- (4-550K) and Q-Band (4-300K) frequencies. Below T_N we observe at Q-Band frequency three very broad absorption bands, which undergo complex changes due to the onset of ferromagnetism at ∼290 K, leaving a single absorption spectrum in the paramagnetic regime. On approaching the insulator-to-metal transition at 360 K from above, we observe a critical narrowing of the ESR signal, which we assign to relaxation processes due to the concomitant spin-state transition. Moreover, the linewidth proved to be frequency dependent indicating a crossover of exchange and resonance frequency.