Tuning the magnetic entropy change of Ni50−xMn35+xIn15 alloys by varying the Mn content

Abstract

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Magnetic entropy change involving martensitic transition in NiMn-based Heusler alloys

“…However, before the FM transition in the austenitic phase is completed, the martensitic transformation has already taken place at T M ∼ 314 K with a hysteresis about 8 K. Continuously reducing the temperature leads to the FM ordering of the martensitic phase with Curie temperature T M C ∼ 170 K. At temperatures lower than 135 K, a large separation between ZFC and FC magnetizations is observed, which is understandable considering the magnetic anisotropy in the martensitic state and the existence of both FM and AFM clusters. [41] T/K [65] With increasing Mn content, T M decreases but T M C increases, which is in accord with the general dependence of the transition temperatures on the valence electron concentration in NiMn-based alloys. [40,41] The inset of Fig.…”

“…More importantly, it can remarkably reduce the thermal hysteresis. Figure 10 displays the temperature dependent ZFC and FC magnetizations [65] From Fig. 10, one can also find that the Ni 51 Mn 49−x In x alloys show a very small thermal hysteresis (< 2 K) around T M .…”

“…The temperature dependent ZFC-FC magnetizations [65] measured under 0.05 T, 1 T, and 5 T indicates that the martensitic temperature T M locates at 260 K and 214 K under magnetic fields 0.05 T and 5 T, respectively.…”

“…By changing the Mn content but fixing the In content, a field-induced structural transition was realized in a modified composition, with T M at 285 K. Associated with the field-induced metamagnetic behavior, a huge ∆S with a wide temperature span was observed near room temperature. Figure 7 shows the temperature dependent zero-field cooling (ZFC) and field cooling (FC) magnetizations [65] under 0.05 T for samples of x = 0, 3, 4. For the x = 0 sample, the magnetization gradually increases on cooling, and the appearance of a small cusp indicates the onset of the FM order of the austenitic phase.…”

“…The lattice parameter of Ni 51 Shown in Fig. 12 are the temperature dependent ZFC and FC magnetizations [65] Although the magnetization difference across the martensitic transition, ∆M, is somewhat reduced by inserting H atoms, the driving rate shows a small increase, indicating that the insertion of H atoms makes the martensitic transition easier to drive under the same Zeeman energy. The previous studies [79] show that a very small change of the Mn-Mn distance will greatly affect the magnetic properties of the sample.…”