Modifying the transition temperature, 120 K ≤ T ≤ 1150 K, of amorphous FeCoSc with simultaneous alteration of fluctuation of exchange integral up to zero.

Amorphous (a-) FeCoSc alloys have been produced by rapid quenching from the melt. The Curie temperature, T 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 on the atomic spacing can be explained by the empirical Bethe-Slater curve. The value of T of a- FeCoSc, determined by the above theoretical approaches is 1150 K, which is the highest T 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, 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-FeSc without Co, however, the fluctuation of the exchange integral is dominant only at zero external field, B = 0. At B = 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 = 9 T the frozen magnetic clusters control the behaviour of the reduced magnetization as function of T/T. In contrast to other ferromagnetic alloys, where the flattening of M(T)/M(0) is characteristic for an amorphous structure, the a- FeCoSc does not exhibit any trace of the fluctuation of the exchange integral.