Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGd

F. A. Garcia

¹

,

P. A. Venegas

²

,

P. G. Pagliuso

³

et al.

Abstract

We report electron spin resonance (ESR) measurements in the Gd 3+ doped semiconducting filled skutterudite compound Ce1−xGdxFe4P12 (x ≈ 0.001). As the temperature, T , varies from T ≃ 150 K to T ≃ 165 K the Gd 3+ ESR fine and hyperfine structures coalesce into a broad inhomogeneous single resonance. At T ≃ 200 K the line narrows and as T increases further the resonance becomes homogeneous with a thermal broadening of 1.1(2) Oe/K. These results suggest that the origin of these features may be associated to a subtle interdependence of thermally activated mechanisms that combine: i) an increase with T of the density of activated conduction-carriers across the Tdependent semiconducting pseudogap; ii) the Gd 3+ Korringa relaxation process due to an exchange interaction, J f d S.s, between the Gd 3+ localized magnetic moments and the thermally activated conduction-carriers and; iii) a relatively weak confining potential of the rare-earth ions inside the oversized (Fe2P3)4 cage, which allows the rare-earths to become rattler Einstein oscillators above T ≈ 148 K. We argue that the rattling of the Gd 3+ ions, via a motional narrowing mechanism, also contributes to the coalescence of the ESR fine and hyperfine structure.

Collapse of the Gd3+ ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor CeFeVenegas1, Garcia2, García3 et al. 2016Phys. Rev. BSelf Cite80100View full textAdd to dashboardCite

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