Abstract
Amorphous (a-) Fe90−xCoxSc10 alloys have been produced by rapid quenching from the melt. The Curie temperature, TC, 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 TC on the atomic spacing can be explained by the empirical Bethe-Slater curve. The value of TC of a- Fe5Co85Sc10, determined by the above theoretical approaches is 1150 K, which is the highest TC ever measured for amorphous alloys. The flattening of the measured normalized magnetization, M(T)/M(0), as a function of the reduced temperature, T/TC, 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-Fe90Sc10 without Co, however, the fluctuation of the exchange integral is dominant only at zero external field, Bex = 0. At Bex = 9 T, however, the fluctuation of the exchange integral has no conspicuous effect on the reduction of the magnetization. It is shown that at Bex = 9 T the frozen magnetic clusters control the behaviour of the reduced magnetization as function of T/TC. In contrast to other ferromagnetic alloys, where the flattening of M(T)/M(0) is characteristic for an amorphous structure, the a- Fe5Co85Sc10 does not exhibit any trace of the fluctuation of the exchange integral.
Highlights
In the case of a-Fe90Sc10 without Co, the fluctuation of the exchange integral is dominant only at zero external field, Bex = 0
FeCo-based amorphous alloys have among all transition metals based ferromagnetic amorphous alloys the highest Curie temperature[2]
It has been reported that a- Co90Sc102 has the highest TC ≈ 1000 K among the amorphous transition metals
Summary
Received: 30 July 2018 Accepted: 28 November 2018 Published: xx xx xxxx temperature, 120 K ≤ Tc ≤ 1150 K, of amorphous Fe90−xCoxSc10 with simultaneous alteration of fluctuation of exchange integral up to zero. Efforts have been made to produce soft magnetic materials with high saturation magnetization, high Curie temperature, low magnetic coercivity, high permeability and low magnetostriction These aims are mostly achieved by Co-based amorphous alloys. It has been reported that a-Co90Sc10 has a high Curie temperature (Tc > 860 K) and good soft magnetic properties[2] This investigation is based on objectives aimed at producing amorphous alloys with high transition temperature and simultaneous reduction of variations of magnetization curve as a function of temperature to approximately zero in the range T = 300 ± 100 K. As with most transition metals[8], assuming that the following equation, M(T)/M(0) = Bhf(T)/Bhf(0), is authentic between the magnetization and average magnetic hyperfine field, the magnetic behaviour as a function of temperature of a- Fe90Sc10 will be discussed in this report.
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