Relevance of Ferromagnetic Correlations for the Electron Spin Resonance in Kondo Lattice Systems

Krellner, C.; Förster, Tobias; Jeevan, H. S.; Geibel, C.; Sichelschmidt, J.

doi:10.1103/physrevlett.100.066401

Cited by 82 publications

(141 citation statements)

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“…Striking examples for such a situation are the CESR signals in Pd [18] and TiBe 2 [19]. For Kondo lattice systems there is strong experimental evidence that FM correlations between the Kondo ions are essential for narrow observable ESR signals [20]. For YbRh 2 Si 2 in the T − B parameter domain studied in the present work FM fluctuations have been found by 29 Si-NMR [3].…”

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confidence: 68%

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 in Ref. [4]): At temperatures above T C the linewidth of the polycrystals is dominated by the H⊥c signal of the grains. Below T C the strong shift of the resonance field due the FM transition separates the signals, and the linewidth is dominated by the H c component.…”

Section: Temperature and Frequency Behaviour Of The Esr Linewidthmentioning

confidence: 99%

Electron spin resonance of the ferromagnetic Kondo lattice CeRuPO

Förster¹,

Sichelschmidt²,

Krellner³

et al. 2010

J. Phys.: Condens. Matter

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Abstract. The spin dynamics of the ferromagnetic Kondo lattice CeRuPO is investigated by Electron Spin Resonance (ESR) at microwave frequencies of 1, 9.4, and 34 GHz. The measured resonance can be ascribed to a rarely observed bulk Ce 3+ resonance in a metallic Ce compound and can be followed below the ferromagnetic transition temperature T C = 14 K. At T > T C the interplay between the RKKYexchange interaction and the crystal electric field anisotropy determines the ESR parameters. Near T C the spin relaxation rate is influenced by the critical fluctuations of the order parameter.

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“…In heavy fermion system CeRuPO, FM correlations is define by the ESR signal. 28 At low temperature below 10 K (Curie temperature = 15 K), ESR of CeRuPO shows similar diplike signals at low fields as well as NiBi 3 . This diplike signal should be related to ferromagnetic moment fluctuations.…”

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Surface-induced magnetic fluctuations in a single-crystal NiBi3superconductor

et al. 2012

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We report anistropy in superconducting and normal state of NiBi3 single crystals with Tc = 4.06 K. The magnetoresistance results indicate the absence of scattering usually associated with ferromagnetic metals, suggesting the absence of bulk long range magnetic order below 300 K. However, the electron spin resonance results demonstrate that ferromagnetism fluctuations exist on the surface of the crystal below 150K.

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Relevance of Ferromagnetic Correlations for the Electron Spin Resonance in Kondo Lattice Systems

Cited by 82 publications

References 24 publications

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

Evolution of the Kondo State ofYbRh2Si2Probed by High-Field ESR

Electron spin resonance of the ferromagnetic Kondo lattice CeRuPO

Surface-induced magnetic fluctuations in a single-crystal NiBi3superconductor

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