Electron spin resonance in YbRh2Si2: The role of the residual linewidth

Wykhoff, J.; Sichelschmidt, J.; Ferstl, J.; Krellner, C.; Geibel, C.; Steglich, F.; Fazlishanov, I.; Nidda, H.-A. Krug von

doi:10.1016/j.physc.2007.03.123

Cited by 18 publications

(27 citation statements)

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“…That is why the observation of a narrow electron spin resonance (ESR) signal in the Kondo state of YbRh 2 Si 2 was very surprising [7]. While the reported pronounced anisotropy of the signal is indeed in accordance with an ESR of localized Yb 3+ 4f moments, a non-local picture is suggested by the observation of this signal down to the lowest accessible temperatures of 0.69 K [8] where the single ion Kondo effect is expected to screen the magnetic moments. On the other hand the conduction electron ESR seems also unlikely because in this compound comprising heavy metal elements the spin-orbit (SO) coupling drastically shortens the electron spin lifetime [9].…”

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Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

et al. 2009

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An electron spin resonance (ESR) study of the heavy fermion compound YbRh2Si2 for fields up to ∼ 8 T reveals a strongly anisotropic signal below the single ion Kondo temperature TK ∼ 25 K. A remarkable similarity between the T -dependence of the ESR parameters and that of the specific heat and the 29 Si nuclear magnetic resonance data gives evidence that the ESR response is given by heavy fermions which are formed below TK and that ESR properties are determined by their field dependent mass and lifetime. The signal anisotropy, otherwise typical for Yb 3+ ions, suggests that, owing to a strong hybridization with conduction electrons at T < TK, the magnetic anisotropy of the 4f states is absorbed in the ESR of heavy quasiparticles. Tuning the Kondo effect on the 4f states with magnetic fields ∼ 2 − 8 T and temperature 2 − 25 K yields a gradual change of the ESR g-factor and linewidth which reflects the evolution of the Kondo state in this Kondo lattice system. PACS numbers: 71.27.+a, 75.20.Hr, Strong electron-electron (EE) interactions in metals yield a fascinating variety of novel and often interrelated quantum phenomena, such as quantum phase transitions, breakdown of the Landau Fermi-liquid (LFL) state, unconventional superconductivity, etc. (for an overview see, e.g., [1]). In intermetallic compounds where 4f (5f ) magnetic ions (e.g. Yb, Ce, U etc.) build up a regular Kondo lattice, strong EE correlations are established by the coupling of local f -magnetic moments with the conduction electrons (CE). As a consequence, a large effective mass enhancement of the quasiparticles (QP) hallmarks the properties of paramagnetic heavy fermion metals. A competing interaction, the so-called RKKY-interaction between the local f -states via the sea of CE, favors a magnetically ordered ground state.An important realization of a system where the delicate balance between Kondo and RKKY interactions can be investigated is the intermetallic compound YbRh 2 Si 2 where antiferromagnetic order, quantum criticality, heavy fermion-and non-LFL (NFL) behavior can be tuned by a magnetic field B and temperature T [2,3,4,5,6] (Fig. 1). In the parameter domain where these remarkable electronic crossovers take place a strong hybridization of 4f electrons with CE significantly broadens the otherwise atomically sharp f -states. That is why the observation of a narrow electron spin resonance (ESR) signal in the Kondo state of YbRh 2 Si 2 was very surprising [7]. While the reported pronounced anisotropy of the signal is indeed in accordance with an ESR of localized Yb 3+ 4f moments, a non-local picture is suggested by the observation of this signal down to the lowest accessible temperatures of 0.69 K [8] where the single ion Kondo effect is expected to screen the magnetic moments. On the other hand the conduction electron ESR seems also unlikely because in this compound comprising heavy metal elements the spin-orbit (SO) coupling drastically shortens the electron spin lifetime [9].To unravel a controversial nature of this resonance response w...

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Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

et al. 2009

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“…2 we used two samples with similar linewidth and similar residual resistivity ratio. As reported earlier [14] the linewidth at a given temperature is related to the residual resistivity ratio which in turn determines the residual linewidth DB 0 (temperature-linear part of DB extrapolated to zero temperature). The temperature dependence of the linewidth obeys the scaling DB Ã ¼ ðDB À DB 0 Þ=DB 0 , i.e.…”

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confidence: 57%

“…The temperature dependence of the linewidth obeys the scaling DB Ã ¼ ðDB À DB 0 Þ=DB 0 , i.e. DB Ã ðTÞ for all investigated YbRh 2 Si 2 , for La-doped YbRh 2 Si 2 [14] and also for 174 YbRh 2 Si 2 collapse onto one single curve. This scaling provides evidence that the lattice relaxation of a strongly coupled Yb 3þ -conduction electron system is an important ingredient for understanding the ESR linewidth in YbRh 2 Si 2 .…”

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confidence: 82%

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On the local and itinerant properties of the ESR in YbRh₂Si₂

Wykhoff

Sichelschmidt

Lapertot

et al. 2007

Science and Technology of Advanced Materials

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Below the Kondo temperature the heavy Fermion compound YbRh 2 Si 2 shows a well defined electron spin resonance (ESR) with local Yb 3þ properties. We report a detailed analysis of the ESR intensity which gives information on the number of ESR active centers relative to the ESR of well localized Yb 3þ in YPd 3 :Yb. The ESR lineshape is investigated regarding contributions from itinerant centers. From the ESR of monoisotopic 174 YbRh 2 Si 2 we could exclude unresolved hyperfine contributions to the lineshape.

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“…As in the early work of Tien et al [8] the observation of a narrow Yb 3þ ESR in the intermediate valence compound of YbCuAl and, recently, in a dense Kondo system below T K were unexpected results [7]. Nevertheless, various reports were already published on the ESR of Yb 3þ in stoichiometric YbRh 2 Si 2 [9], YbIr 2 Si 2 [10], and YbRh 2 Si 2 doped with non-magnetic impurities as Ge [11] and La [12]. Also, the ESR of Ce 3þ in dense Kondo systems was communicated [13].…”

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confidence: 88%

Field-dependent collective ESR mode in YbRh 2 Si 2

Holanda

Duque

Bittar

et al. 2009

Physica B: Condensed Matter

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a b s t r a c tElectron spin resonance (ESR) experiments in YbRh 2 Si 2 Kondo lattice ðT K C25 KÞ at different field/ frequencies ð4:1rnr34:4 GHzÞ and H ?c revealed: (i) a strong field dependent Yb 3þ spin-lattice relaxation, (ii) a weak field and T-dependent effective g-value, (iii) a suppression of the ESR intensity beyond 15% of Lu-doping, and (iv) a strong sample and Lu-doping ðr15%Þ dependence of the ESR data. These results suggest that the ESR signal in YbRh 2 Si 2 may be due to a coupled Yb 3þ -conduction electron resonant collective mode with a subtle field-dependent spins dynamic.

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Electron spin resonance in YbRh2Si2: The role of the residual linewidth

Cited by 18 publications

References 8 publications

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

On the local and itinerant properties of the ESR in YbRh₂Si₂

Field-dependent collective ESR mode in YbRh 2 Si 2

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Electron spin resonance in YbRh2Si2: The role of the residual linewidth

Cited by 18 publications

References 8 publications

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

On the local and itinerant properties of the ESR in YbRh2Si2

Field-dependent collective ESR mode in YbRh 2 Si 2

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Product

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On the local and itinerant properties of the ESR in YbRh₂Si₂