Exchange-narrowed anisotropy contribution to the EPR width and shift in the Ag-Mn spin-glass

The EPR linewidth in the paramagnetic phase (T>Tg) of AgMnₓ and AgMnₓSby contains a term which increases near Tg as a power law in (T-Tg)Tg. The magnitude of the power-law contribution varies linearly with y. These results are interpreted in terms of exchange narrowing of an anisotropic, Dyaloshinski-Moriya interaction. Both width and shift depend strongly on frequency between 1 and 9.6 GHz. The shift behaves neither as a pure g-value shift nor as a frequency-independent internal field. Results are compared with the microscopic theory of Levy, Morgan-Pond, and Raghavan, and with a phenomenological approach.