Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 39: Correlated Electrons: Heavy Fermions 1

TT 39.2: Vortrag

Donnerstag, 26. März 2009, 10:00–10:15, HSZ 304

Tuning the Kondo Effect in YbRh₂Si₂: Electron Spin Resonance under Pressure and Doping — •Jan Wykhoff¹, D. V. Zakharov², H.-A. Krug von Nidda², I. Fazlizhanov³, J. Sichelschmidt¹, C. Krellner¹, C. Geibel¹, A. Loidl², and F. Steglich¹ — ¹MPl for Chemical Physics of Solids, D-01187 Dresden — ²EP V, EKM, University of Augsburg, D-86135 Augsburg — ³E. K. Zavoisky Physical Technical Institute, 420029 Kazan, Russia

The observation of a well defined Electron Spin Resonance (ESR) signal below the Kondo temperature T_K in the heavy-fermion compound YbRh₂Si₂ refutes a common believe that concentrated rare earth ions in Kondo-lattice intermetallic compounds would be ESR silent in the Kondo regime. The signal shows distinct properties of the Yb³⁺ 4f spin and, hence, should contain valuable microscopic information on the dynamical Kondo coupling to the conduction electrons [1]. We investigated the effect of tuning the 4f - conduction electron hybridization strength by Co-doping and hydrostatic pressure up to 3 GPa. Both stabilize antiferromagnetic order, lead to a reduction of T_K, and yield pronounced changes in the ESR parameters. By comparing the quantitatively different effect of pressure and Co doping on the ESR parameters we found a relation of the zero temperature residual ESR linewidth to the residual resistivity and the linear in temperature slope of the linewidth as was similarly reported for the La-doping case [1].

[1] J.W. et al. Physica C 460-462, 686 (2007); J.Sci.Tech.Adv.Mat. 8 389 (2007); J.S. et al. Phys. Rev. Lett. 91 156401 (2003).