Coexistence of Two Kinds of Magnetic Excitations in Concentrated Spin-Glass Alloy Fe₆₅(Ni_0.866Mn_0.134)₃₅

Abstract

Spin-wave excitations in reentrant spin-glass (RSG) materials have been a controversial issue for a long time. In one group of materials, spin-wave stiffness constant D and spin-wave amplitude A_s decrease as temperature decreases toward the spin-glass transition temperature in accordance with the decrease of magnetization. In another group of materials, the temperature variations of D and A_s are opposite to those observed in the former group. The coexistence of two kinds of spin-waves has been observed in the RSG alloy Fe₆₅(Ni_0.866Mn_0.134)₃₅. Temperature variations of D and A_s for each spin-wave are similar to those of each spin-wave observed in the two groups of materials. The origin of the two kinds of spin-wave excitations observed in different groups of RSG materials is attributed to the presence of spin-waves in finite-size magnetic clusters and in an infinite ferromagnetic network.