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Abstract:
de Haas–van Alphen quantum oscillations have been seen for the first time in single crystals of LaAl2 heavily doped with the magnetic impurities Ce and Gd. Spin-split zeros have been detected on the Γ-centered sheet of the Fermi surface in pure LaAl2. These change to spin-split minima in the doped crystals. From these observations, along with orbitally averaged effective-mass measurements, estimates have been made of the g-value shift and the spin-dependent scattering due to the presence of the rare-earth impurities. Measurements of the scattering rate were made, as a function of temperature, in the 0.5 at. % Ce and the 0.5 at. % Gd impurity-doped crystals, for two orbits. An orbit selected for high s-p–wave character showed no temperature dependence for either impurity, whereas an orbit selected for high d-f character showed Kondo-like behavior for both the Ce- and the Gd-doped crystals. This is in contrast to the resistivity, which has a Kondo-like behavior for Ce but not for Gd doping. Dingle-temperature anisotropy has been studied on the Γ-centered sheet of the Fermi surface for the 0.3 at. % Ce and the 0.5 at. % Gd impurity-doped crystals, with use of three orbits of qualitatively different symmetry character. Data from the Ce-doped sample indicate the presence of extreme spin-dependent scattering for the orbit passing through four 〈100〉 directions in k space, which include a strong f-wave component. This behavior is consistent with the spin-split-minimum rotation diagrams, which show increased spin-dependent scattering as one proceeds in the direction of increasing f-wave character from 〈111〉 to 〈100〉 in the (110) plane.
