High-field susceptibility and spin wave stiffness constant of Co-Y amorphous alloys

Several Co-Y amorphous alloys with thickness about 0.2 mm were prepared by dc high-rate sputtering. Fundamental magnetic properties and the density were investigated, and the difference in magnetic properties between amorphous and crystalline states is discussed. Amorphous alloys below 33.3% Y (Co2Y) exhibit a markedly small high-field susceptibility in analogy with that of strong ferromagnets. The significant difference in the magnetic moment between amorphous ahd crystalline states occurs above 25% Y (Co3Y). The density obtained by the Archimedean method also shows a large difference of about 7∼9% in both states above the same composition. These differences are interrelated with each other because the magnetic moment is easily affected by the atomic distance. The spin wave stiffness constant D in the amorphous state is extremely large. The ferromagnetic state is retained up to about 50% Y and the spin glass behavior and the enhancement of dc susceptibility are observed above this composition in the amorphous state.