Resonance and relaxation effects in solid-solution alloys

Electron-spin-resonance measurements on solid-solution alloys of Au-Fe and some other dilute spin-glass alloys are presented. A consideration of the spin relaxation in terms of the spin-glass Hamiltonian shows that the linewidth can be understood in terms of motional or exchange narrowing by interactions between spins prior to the spin-glass freezing temperature. In Au-Fe alloys above the percolation limit, the spin of the finite cluster provides a powerful relaxation channel for the infinite ferromagnetic cluster through which energy flow to the lattice is possible. Freezing of the finite clusters influences the relaxation and so does not help to secure thermal equilibrium between the spin system and the lattice. Hence, the linewidth-temperature curves display maxima. Non-intrinsic effects associated with sample geometry are also considered.