Spin dynamics of the concentrated spin glass Y(Mn0.9Al0.1)2

Inelastic-neutron-scattering measurements employing polarization analysis have been performed on a pseudobinary intermetallic compound Y(${\mathrm{Mn}}_{0.9}$ ${\mathrm{Al}}_{0.1}$ ${)}_2$, which transforms to spin-glass state below ${\mathit{T}}_{\mathrm{SG}}$=42 K. The temperature variation of the energy width of the scattered neutron spectrum follows an Arrhenius law over a wide temperature range, and the width above ${\mathit{T}}_{\mathrm{SG}}$ is much larger when compared with other concentrated spin glasses. The collapse of helical magnetic order caused by a slight dilution of the magnetic Mn atoms with nonmagnetic Al atoms and the very large excitation spectrum above ${\mathit{T}}_{\mathrm{SG}}$ show that the itinerant character of magnetic electrons as well as the strong frustrations of magnetic interactions play an important role in this material. The importance of proper treatment of magnetic moments, taking into account the itinerent character of the magnetic electrons in metallic spin glasses, is discussed.