Suppression of spin fluctuations by the magnetic field and Co concentration in amorphous Fe90-xCoxZr10 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(0, H)] = 1 - A(H)T-2 in the intermediate-temperature range and as [M(T, H)/M(0, H)](2) = 1-A'(H)T-4/3 for temperatures in the vicinity of T, (Curie point) but still away from criticality. Suppression of spin fluctuations by either the Co concentration in a-Fe90-xCoxZr10 alloys or the held H for a given composition in the a-Fe90-xCoxZr10 and 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 T-C(-2) and T-C(-4/3), respectively, A(H) and A'(H) follow the relation A(H-eff) = A(0)[1 - BHeffpsi] where A = A or A', B = B or B', psi = n or n' and H-eff 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 - mu x(phi)] and n' = 0.50(2) is independent of x in the range less than or equal to x less than or equal to 6. The spin fluctuation model explains many of, but not all, these features.