Suppression of spin fluctuations by the magnetic field and Co concentration in amorphous Fe<SUB>90-x</SUB>Co<SUB>x</SUB>Zr<SUB>10</SUB> alloys

Spin fluctuations manifest themselves in the temperature dependence of the spontaneous magnetization M(T,H=0) or the `in-field' magnetization M(T,H), through a contribution that varies with T as [M(T,H) / M(O,H)] = 1-A(H)T2in the intermediate-temperature range and as [M(T,H) / M(O,H)]2 = 1-A'(H)T4/3for temperatures in the vicinity of Tc(Curie point) but still away from criticality. Suppression of spin fluctuations by either the Co concentration in a-Fe90-xCoxZr10alloys or the field H for a given composition in the a-Fe90-xCoxZr10and a-Fe90+yZr10-y alloy series is, for the first time, monitored through the decrease in the coefficients A and A' with increasing x for H = 0 or with H for fixed x or y. While A(0) and A'(0) scale with TC-2and TC-4/3, respectively, A(H) and A'(H) follow the relation A(Heff) = A(0)[1-BH&#968;eff] where A=A or A' ,B = B or B', or &#968; = n or n'; and Heff is the external field corrected for demagnetization. In contrast with the non-monotonic variation in B and n with x, B' varies with x as B'(x)=B'(0)[1-&#181;x&#934;] and n' = 0.50(2) is independent of x in the range &#8804; x &#8804;. The spin fluctuation model explains many of, but not all, these features