Heusler alloys present a large group of binary, [1][2][3][4][5] ternary, [6][7][8][9][10] or quaternary [11][12][13][14] compounds with a wide variety of physical properties. [15][16][17][18] Thanks to their extensive tunability [19][20][21][22] based on their chemical composition, crystal, or electronic structure, [23][24][25][26][27][28][29] they attract interest in the fundamental and application approach. [30][31][32][33][34] Particularly, spin polarization, [33,35] superconductivity, [36][37][38][39] shape memory, [40][41][42][43][44][45] or magnetocaloric behavior [28,40,[46][47][48][49][50] have triggered significant interest in the experimental and theoretical perspective.Based on the chemical composition and the resulting properties, Heusler alloys, also known as full-Heusler alloys with the stoichiometry X 2 YZ, can be divided into several groups according to their physical properties. [51] Co 2 YZ-based Heusler can be considered the leading group of materials showing high spin polarization (P) or even half metallicity (P ¼ 100%). [52][53][54][55][56][57] However, theoretical and experimental studies point to the high sensitivity of spin polarization on the structural disorder. [58] Here, the L2 1 crystalline phase exhibits the highest structural ordering, essential for achieving the required spin polarization values. [59] In contrast, while the mutual exchange of the atoms on the Y-Z position (B2 disorder) has a low influence on the spin polarization values, the X-Y or X-Y-Z disorders (D0 3 or A2, respectively) may significantly decrease spin polarization values. [55,60,61] The presented disadvantage can be solved by a suitable chemical composition or a proper method of preparation of Heusler alloys. [62,63] Stoichiometric and off-stoichiometric Ni-Mn-Z- [64][65][66] and Ni-Fe-Z-based Heusler alloys [67][68][69] are well-known magnetocaloric, shape memory, or even magnetic shape memory materials. [70,71] The mentioned Heusler alloys undergo a structural transformation from a low-temperature martensitic phase to a high-temperature austenitic phase, [51,[64][65][66][72][73][74] which may significantly influence the magnetic entropy change ΔS M and the intensity of the magnetocaloric effect. [75,76] Additionally, Heusler alloys consist of cheap elements like Ni, Fe, Mn, Co, Ga, and In, and thus may be considered low-cost counterparts for typical magnetocaloric material based on Gd, Rh, or other rare-earth elements. [77][78][79][80][81] Another advantage of the Ni-Mn-Zand Ni-Fe-Z-based Heusler alloys consists in the tunability of their structural and magnetic properties. Depending on the

The magnetic properties and reversibility of the magnetocaloric effect of Ni 50 Mn 35 In 15 have been studied in the vicinity of the phase transition using magnetization and direct adiabatic temperature change (ΔT ad) measurements in magnetic fields up to 14 T. The magnetostructural phase transitions (MSTs) between a martensitic phase (MP) with low magnetization (paramagnetic or antiferromagnetic) and a nearly ferromagnetic austenitic phase were detected from thermomagnetic curves, M(T,H), at the applied magnetic fields up to 5 T. The MST temperature was found to be nearly independent of magnetic field for H< 5T, and shifted to lower temperature with the further increase of magnetic field to 14 T. A large and nearly reversible inverse magnetocaloric effect (MCE) with T ad ~-11 К for a magnetic field change of ΔH = 14 T was observed in the vicinity of the MST. The irreversibility of T ad was found to be 1 K. A direct T ad of +7 K for ΔH = 14 T was detected at the second order ferromagnetic-paramagnetic phase transition. The obtained results have been discussed in terms of the suppression of antiferromagnetic correlations with the application of a strong magnetic field, and a reversibility of the initial magnetic state of the MP with applied magnetic field when the MST coincides with T C .

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The magnetocaloric effect in TbNi2 alloy ribbons synthesized by rapid solidification was investigated. This material crystallizes in a superstructure of the cubic Laves phase structure type C15 (space group F-43m). The saturation magnetization and Curie temperature are MS = 134 ± 2 A m2 kg−1 and TC = 37 ± 1 K, respectively. For a magnetic field change of 5 T, the material shows a maximum magnetic entropy change |ΔSMpeak| = 13.9 J kg−1 K−1, with a full-width at half-maximum δTFWHM = 32 K, and a refrigerant capacity RC = 441 J kg−1. The RC value is similar to those reported for other magnetic refrigerants operating within the temperature range of 10-80 K. Finally, it is worth noting that the use of rapid solidification circumvents the necessity for long-term high-temperature homogenization processes normally needed with these RNi2 alloys.