de Haas-van Alphen effect measurements of the exchange energy and spin-scattering anisotropy in the Kondo alloy copper-iron

Abstract

Unequal scattering of conduction electrons of opposite spin in Cu from Fe impurities has been measured using the wave shape of the de Haas-van Alphen (dHvA) effect. Exchange coupling to the impurity and spin-scattering anisotropy lead to a shift in the relative amplitudes and phases of the harmonics expressed by the Lifshitz-Kosevich formalism of the oscillatory magnetization. Waveform analysis of the dHvA signal from the neck orbit in Cu-93-ppm Fe yields values of the exchange coupling energy which scale linearly with applied field over a range of 30-45 kG, a magnitude equivalent to a $g$-factor shift of 8% (antiferromagnetic) from pure Cu, and no observed temperature dependence over 1-2°K. The spin-scattering anisotropy amounts to about 30% (with electron moment antiparallel to $H$ more strongly scattered), and also shows linear-in-$H$ $T$-independent behavior. Techniques are described to correctly make precise waveshape measurements, even in the presence of skin-depth effects.