Electron spin resonance of Gd in LuAl2

Electron spin resonance spectra of Gd in LuAl2 exhibit significant changes in g shift (Δg) and thermal broadening of the linewidth, (ΔH/ΔT) upon a) varying the concentration of magnetic impurity (Gd); b) adding a second non‐magnetic impurity (Th); and c) lowering the temperature (down to 0.52°K). By reducing the Gd concentration from 2% to 20 ppm we were able to shift the g value and thermal broadening from Δg≃0 and ΔH/ΔT (20±3) G/°K to Δgo=+0.085±0.005 and (ΔH/ΔT)k=(75±10) G/K. The same effect was found by adding Th as a second impurity. Both the g shift and the thermal broadening show appreciable temperature dependence in the range of 0.52<T<6°K. The results are interpreted in terms of Hasegawa's theory for bottleneck and dynamic effects, where the g shift and linewidth can be written as follows: Δg = (δeL/δei)2(1+δeL/δei)2 + (γλχiH/δei)2 Δgo ΔH = (1+δeL/δei) + (γλχiH/δei)2(1+δeL/δei)2 + (γλχiH/δei)2 (δeL/δei) (ΔHΔT)k T Assuming that the exchange interaction Jfs does not depend heavily on the conduction electron momentum transfer, we were able to estimate from the unbottleneck g shift (Δgo) and Korringa rate (ΔH/ΔT)k the electron‐electron exchange enhancement parameter α=0.61 and in turn the exchange interaction Jfs=0.11±0.02 eV.