The magnetic properties of amorphous 3d metal based alloys are diverse, depending on the alloying element. Therefore, it is expected that the nature of spin fluctuations and its influence on the thermal expansion are different from one another for various alloy systems. In the present study, the nature of spin fluctuations and the thermal expansion have been investigated for amorphous Y-TM (TM = Ni, Co, Fe and Mn) alloys prepared by high-rate DC sputtering. The characteristic parameters obtained from the Arrott plots measured with a SQUID magnetometer indicate that the nature of spin fluctuations in the amorphous Y-Ni alloys is similar to that in crystalline weakly ferromagnets. With decreasing Y concentration, the nature of spin fluctuations is located in the interpolation region, being accompanied by the increase in the spontaneous volume magnetostriction. On the other hand, the spin fluctuations in the amorphous Y-Co alloys are relatively localized in the real space, compared with those of amorphous Y-Ni alloys. The amorphous Y-Fe alloys show a large spontaneous volume magnetostriction, indicating a significant variation of the amplitude of spin fluctuations. The thermal expansion coefficient of the amorphous Y-Mn alloys implies that the amplitude of spin fluctuations scarcely depends on the temperature, and the thermal variation of spin fluctuations is observed only in high Mn concentration ranges.
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