HGI Information

Time:2019-04-08Source:HGIView:18次

The Curie temperature, T_{C, }of a-Fe_{90-x}Co_{x}Sc_{10 }was determined using both mean field theory and Landau’s theory of second-order phase transitions in zero and non-zero external fields. 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 isdominant only at zero external field, B_{ex}=0. 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.

Y. Fang, M. Ghafari, T. Feng, et al., **Scientific Reports**, 2018, accepted.

The addition of Co content in Fe_{90-x}Co_{x}Sc_{10} (x = 1, 3, 5 and 7) can not only tune the Curie temperature of these alloys to room temperature, but also simultaneously increase the maximum value of the magnetic entropy change (−ΔS_{M}^{pk}). The −ΔS_{M}^{pk} is 1.40 J/kg K at ΔH = 1.5 T (ΔH: magnetic field change) with x = 7. The maximum refrigerant capacity (RC) is 191.9 J/kg at ΔH = 1.5 T with x = 3, which is higher than that of most of Fe-based amorphous alloys so far discovered. Increasing the ΔH to 2 T, the RC values of these alloys can reach as high as 265.2 J/kg, which is comparable to those detected in crystalline Gd and Gd_{5}Si_{2}Ge_{2}. Enhanced RC values observed in these alloys promise them to be good candidates for near room-temperature magnetic refrigerants.

Y. Fang, G. Peng, T. Feng, et al., **Journal of Non-Crystalline Solids**, 2019, 505, 211.