Modifying the transition temperature, 120 K ≤ T(c) ≤ 1150 K, of amorphous Fe(90−x)Co(x)Sc(10) with simultaneous alteration of fluctuation of exchange integral up to zero

Amorphous (a-) Fe(90−x)Co(x)Sc(10) alloys have been produced by rapid quenching from the melt. The Curie temperature, T(C,) was determined using both mean field theory and Landau’s theory of second-order phase transitions in zero and non-zero external fields. The dependence of T(C) on the atomic spacing can be explained by the empirical Bethe-Slater curve. The value of T(C) of a- Fe(5)Co(85)Sc(10), determined by the above theoretical approaches is 1150 K, which is the highest T(C) ever measured for amorphous alloys. The flattening of the measured normalized magnetization, M(T)/M(0), as a function of the reduced temperature, T/T(C), is explained within the framework of the Handrich- Kobe model. According to this model the fluctuation of the exchange integral is the main reason for the flattening of M(T)/M(0). In the case of a-Fe(90)Sc(10) without Co, however, the fluctuation of the exchange integral is dominant only at zero external field, B(ex) = 0. At B(ex) = 9 T, however, the fluctuation of the exchange integral has no conspicuous effect on the reduction of the magnetization. It is shown that at B(ex) = 9 T the frozen magnetic clusters control the behaviour of the reduced magnetization as function of T/T(C). In contrast to other ferromagnetic alloys, where the flattening of M(T)/M(0) is characteristic for an amorphous structure, the a- Fe(5)Co(85)Sc(10) does not exhibit any trace of the fluctuation of the exchange integral.