Europhys. Lett.
Volume 65, Number 2, January 2004
Page(s) 235 - 241
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 January 2004
Europhys. Lett., 65 (2) , pp. 235-241 (2004)
DOI: 10.1209/epl/i2003-10076-4

Electronic topological transitions, magnetic ordering and the Fermi surfaces of $\chem{Y}$ and the heavy rare earths

S. J. Crowe1, 2, S. B. Dugdale1, Zs. Major1, M. A. Alam1, J. A. Duffy2 and S. B. Palmer2

1  H. H. Wills Physics Laboratory, University of Bristol Tyndall Avenue, Bristol, BS8 1TL, UK
2  Department of Physics, University of Warwick - Coventry, CV4 7AL, UK

(Received 8 August 2003; accepted in final form 12 November 2003)

The magnetic order of the heavy rare earths has long been associated with the presence of a certain feature in the Fermi surface (FS) topology (being common to non-magnetic $\chem{Y}$ also), known as the "webbing". Furthermore, there has been speculation that changes in the observed ordering, brought about by temperature-induced changes in the crystalline c/a ratio, are due to the presence or absence of that webbing feature. Such a simplistic model is appealingly simple in systems where physics of the exchange interaction as a function of composition and temperature is complicated. The $\chem{Gd}$ 1-x $\chem{Y}$ x alloy system exhibits ferromagnetism or helical antiferromagnetism at different compositions and temperatures. We present our experimental measurement of the FS topology of such an alloy at a composition close to the $\chem{Y}$ concentration where helical antiferromagnetism occurs. The data show that the evolution of the FS in $\chem{Gd}$ 1-x $\chem{Y}$ x is different from that predicted by the model based on the c/a ratio, suggesting a less simplistic interpretation.

71.20.Eh - Rare-earth metals and alloys.
71.18.+y - Fermi surface: calculations and measurements; effective mass, g factor.
78.70.Bj - Positron annihilation.

© EDP Sciences 2004