Collapse of the $G{d}^{3+}$ ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor $CeF{e}_4{P}_{12}$

Abstract

Experiments on the $G{d}^{3+}$ Electron Spin Resonance (ESR) in the filled skutterudite $C{e}_{1-x}G{d}_{x}F{e}_4{P}_{12}$ ($x\approx 0.001$), at temperatures where the host resistivity manifests a smooth insulator-metal crossover, provides evidence of the underlying Kondo physics associated with this system. At low temperatures (below $T\approx K$), $C{e}_{1-x}G{d}_{x}F{e}_4{P}_{12}$ behaves as a Kondo-insulator with a relatively large hybridization gap, and the $G{d}^{3+}$ ESR spectra displays a fine structure with lorentzian line shape, typical of insulating media. The electronic gap is attributed to the large hybridization present in the coherent regime of a Kondo lattice, when Ce 4f-electrons cooperate with band properties at half-filling. Mean-field calculations suggest that the electron-phonon interaction is fundamental at explaining the strong 4f-electron hybridization in this filled skutterudite. The resulting electronic structure is strongly temperature dependent, and at about $T^{\ast }\approx 160K$ the system undergoes an insulator-to-metal transition induced by the withdrawal of 4f-electrons from the Fermi volume, the system becoming metallic and non-magnetic. The $G{d}^{3+}$ ESR fine structure coalesces into a single dysonian resonance, as in metals. Still, our simulations suggest that exchange-narrowing via the usual Korringa mechanism, alone, is not capable of describing the thermal behavior of the ESR spectra in the entire temperature region ($4.2$ - $300$ K). We propose that temperature activated fluctuating-valence of the Ce ions is the missing ingredient that, added to the usual exchange-narrowing mechanism, fully describes this unique temperature dependence of the $G{d}^{3+}$ ESR fine structure observed in $C{e}_{1-x}G{d}_{x}F{e}_4{P}_{12}$.

arXiv comment19 pages, 6 figures

References in corpus (17)

• Unusual behaviors in the transport properties of REFe${}_4$P${}_{12}$ (RE: La, Ce, Pr, and Nd)
• Topological Crystalline Kondo Insulator in Mixed Valence Ytterbium Borides
• Transport properties in CeOs${}_4$Sb${}_{12}$: Possibility of the ground state being semiconducting
• Crystal-field ground state of the orthorhombic Kondo insulator CeRu2Al10
• Optical Properties of MFe_4P_12 filled skutterudites
• Anisotropic spin-dynamics in the Kondo semiconductor CeRu2Al10
• Magnetic and Thermodynamic Properties of the Three-Dimensional Periodic Anderson Hamiltonian
• Anisotropic optical conductivity of the putative Kondo insulator CeRu${}_4$Sn${}_6$
• Phase Diagram of the 1D Anderson Lattice
• Suppression of antiferromagnetic order and hybridization gap by electron- and hole-doping in the Kondo semiconductor CeOs${}_2$Al${}_{10}$
• Magnetic instability induced by Rh-doping in Kondo semiconductor CeRu${}_2$Al${}_{10}$
• Temperature dependent band structure of the Kondo insulator
• Contrasting electron and hole doping effects on the spin gap of the caged type Kondo semimetal CeOs${}_2$Al${}_{10}$: A muon spin relaxation and inelastic neutron scattering investigation
• Ferromagnetism and phase separation in one-dimensional d-p and periodic Anderson models
• Electronic structure of semiconducting CeFe${}_4$P${}_{12}$: Strong hybridization and relevance of single-impurity Anderson model
• Thermally activated exchange narrowing of the Gd3+ ESR fine structure in a single crystal of Ce1-xGdxFe4P12 (x = 0.001) skutterudite
• Spin dynamics of S-state ions in the filled skutterudites La1-xRx$Pt4Ge12 (R= Gd, Eu)

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• Hard X-ray spectroscopy of the itinerant magnets $R$Fe${}_4$Sb${}_{12}$ ($R=$Na, K, Ca, Sr, Ba)
• Slow crystalline electric field fluctuations in the Kondo lattice SmB${}_6$
• Phonon Scattering Mechanism in Thermoelectric Materials Revised via Resonant X-ray Dynamical Diffraction