Neutron Scattering Study of Concentrated Spin Glass Alloys Fe₆₅(Ni1-xMnx)₃₅

Magnetic susceptibility and neutron scattering measurements have been made on a pseudo-binary alloy system Fe 65 (Ni 1- x Mn x ) 35 with x =0.134 and x =0.22. Low field susceptibility measurements have shown that these alloys transform to a low temperature spin-glass phase from a ferromagnetic ( x =0.134) or a paramagnetic ( x =0.22) phase. In the alloy with x =0.134, spin-wave excitations have been observed in the spin-glass phase as well as in the ferromagnetic phase. The spin-wave stiffness constant does not change appreciably at the spin-glass freezing temperature. Spin-wave excitations have also been observed in the alloy with x =0.22 over the wide temperature range in the spin-glass and the paramagnetic phases.