| Popis: |
In this paper, we introduce a novel calculation method of magnetic entropy change in an arbitrary ferromagnetic system based on the Landau model for Gibbs free energy and the Arrott–Noakes equation, −ΔSM=11γ+1dA(T)dTM1γ+1−MS1γ+1+11β+1γ+1dB(T)dTM1β+1γ+1−MS1β+1γ+1−M−MSH1γH1−1γ. This theoretical study was applied to TbFeSi (TFS) and DyFeSi (DFS) intermetallic compounds. First, the critical exponents (β; γ) are found as (0.46; 1.08) and (0.26; 1) for TFS and DFS, respectively. Second, the limitations of the Arrott–Noakes equation in simulating the hole −ΔSM(H, T) curves were discussed. Third, the usefulness of the new method reported earlier predicted large RCP values of around 810 and 779 J kg−1 under a 10 T magnetic field for TFS and DFS samples, respectively. |
