Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 4: Schwere Fermionen, Kondo-Systeme

TT 4.8: Vortrag

Montag, 24. März 2003, 16:30–16:45, HSZ03

ESR Study of the Heavy-Fermion Compound YbRh₂Si₂ — •V.A. Ivanshin^1,2, J. Sichelschmidt¹, J. Ferstl¹, C. Geibel¹, and F. Steglich¹ — ¹Max-Planck-Institut für Chemische Physik fester Stoffe, D-01187 Dresden, Germany — ²MRS Laboratory, Kazan State University, 420008 Kazan, Russia

The heavy-fermion (HF) compound YbRh₂Si₂ shows non-Fermi-liquid (NFL) effects below T<10 K. The NFL behavior is related to the proximity of a magnetic instability. Weak antiferromagnetic order at ambient pressure is observed at the extremely low ordering temperature of ≃70 mK. A highly anisotropic magnetic response indicates that Yb³⁺-moments are forming an No-dqeasy-planeNo-dq square lattice perpendicular to the crystallographic c-direction [1].

We present the first observation of electron spin resonance (ESR) in YbRh₂Si₂ single crystals. High-quality single crystalline platelets were grown from In flux. The ESR measurements were performed with a Bruker ELEXSYS E500 spectrometer at X- and Q-band frequencies. Below T = 17 K we detected strongly anisotropic ESR signals of Dysonian lineshape (g_∥ < 0.4; g_⊥ = 3.4) which are ascribed to Yb³⁺-ions (4f¹³). To our knowledge this is the first report of ESR in an undoped Yb-based HF compound. We investigated the relation of the ESR spectra to the Kondo effect in YbRh₂Si₂. A deviation from the linear thermal broadening was observed at temperatures above 9 K. Possible relaxation mechanisms are discussed.

[1] P. Gegenwart et al., Phys. Rev. Lett. 89, 056402 (2002)