Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1-xGdxFe4P12(x-0.001) skutterudite
- Author(s): Garcia, FA
- Venegas, PA
- Pagliuso, PG
- Rettori, C
- Fisk, Z
- Schlottmann, P
- Oseroff, SB
- et al.
Published Web Locationhttps://doi.org/10.1103/PhysRevB.84.125116
We report electron spin resonance (ESR) measurements in the Gd3+doped semiconducting filled skutterudite compound Ce1-xGdxFe4P12(x-0.001). As the temperature T varies from T- 150 K to T- 165 K, the Gd3+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 with a subtle interdependence of thermally activated mechanisms that combine: (i) an increase with T of the density of activated conduction carriers across the T-dependent semiconducting pseudogap; (ii) the Gd3+Korringa relaxation process due to an exchange interaction JfdS.s between the Gd3+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)4cage, which allows the rare earths to become rattler Einstein oscillators above T- 148 K. We argue that the rattling of the Gd3+ions, via a motional narrowing mechanism, also contributes to the coalescence of the ESR fine and hyperfine structure. © 2011 American Physical Society.
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