Electronic topological transitions, magnetic ordering and the Fermi surfaces of and the heavy rare earthsS. 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 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 1-x 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 concentration where helical antiferromagnetism occurs. The data show that the evolution of the FS in 1-x 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