Europhys. Lett.
Volume 76, Number 5, December 2006
Page(s) 938 - 944
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2006
Europhys. Lett., 76 (5), pp. 938-944 (2006)
DOI: 10.1209/epl/i2006-10339-6

Charge localization due to RKKY interaction in the spin-glass $\chem{AuFe}$

B. Gorshunov1, 2, A. S. Prokhorov2, S. Kaiser1, D. Faltermeier1, S. Yasin1, M. Dumm1, N. Drichko1, 3, E. S. Zhukova2, I. E. Spektor2, S. Vongtragool4, 5, M. B. S. Hesselberth4, J. Aarts4, G. J. Nieuwenhuys4, 5 and M. Dressel1

1  1. Physikalisches Institut, Universität Stuttgart - 70550 Stuttgart, Germany
2  Prokhorov General Physics Institute, Russian Academy of Sciences - Moscow, Russia
3  Ioffe Physico-Technical Institute - St. Petersburg, Russia
4  Kamerlingh Onnes Laboratory, Leiden University - Leiden, The Netherlands
5  Research Department Condensed Matter Research with Neutrons und Muyons Paul Scherrer Institute - Villigen, Switzerland

received 21 September 2006; accepted 5 October 2006
published online 1 November 2006

Measurements of the electrodynamic response of spin-glass $\chem{AuFe}$ films in comparison with pure gold films are performed at frequencies from 0.3$\un{THz}$ ( $10\un{cm^{-1}}$) up to 1000$\un{THz}$ ( $33000\un{cm^{-1}}$) using different spectroscopic methods. At room temperature the spectra of pure gold and of $\chem{AuFe}$ are typically metallic with the scattering rate of carriers in $\chem{AuFe}$ being significantly enlarged due to scattering on localized magnetic moments of Fe ions. In the spin-glass phase of $\chem{AuFe}$ at $T=5\un{K}$ a pseudogap in the conductivity spectrum is detected with the magnitude close to the Ruderman-Kittel-Kasuya-Yosida (RKKY) energy for $\chem{AuFe}$: $\Delta_{\rm RKKY}\approx 2.2\un{meV}$. The origin of the pseudogap is associated with partial localization of electrons which mediate the RKKY interaction between localized magnetic Fe centers.

75.50.Lk - Spin glasses and other random magnets.
71.55.Jv - Disordered structures; amorphous and glassy solids.
72.15.Rn - Localization effects (Anderson or weak localization).

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