Martensitic Transformation, Magnetic and Mechanical Characteristics in Unidirectional Ni–Mn–Sn Heusler Alloy

Abstract

A textured structure of Ni–Mn–Sn Heusler alloy with [001] preferred orientation has been grown by the directional solidification method. The crystal exhibits a single austenite phase L21 cubic structure (a = 5.997 Å) at room temperature. Magnetization and electronic transport measurements reveal the phase transformation characteristics. The maximum values of magnetic entropy change determined by Maxwell’s thermodynamic relation during the structural and magnetic phase transformations are 3.5 J/kg·K and −4.1 J/kg·K, and the total effective refrigerant capacity reaches about 314 J/kg (5 T). The evident reduction in hysteresis loss and broad operating temperature window provide a greater prospect for improving the cyclic stability of refrigeration and optimizing the application of such a magnetic refrigeration material. Both magnetoresistance (−18%, 5 T) and exchange bias field (302 Oe, 2 K) have also been investigated to understand the nature of phase transformations and exchange interactions. Furthermore, as the material exhibits excellent mechanical properties (1068 MPa, 9.0%), our experimental results provide a new reference for the application of Ni–Mn–Sn Heusler alloys.

Crystal Structure and Properties of Heusler Alloys: A Comprehensive Review

“…However, the coincidence of these thermo-magnetization curves close to the Curie temperatures of austenite and martensite phases, T C A and T C M , respectively, indicates that these transitions are of the second order. From these curves, the typical structural and transition temperatures are noticed as Ms = 261.0 K, Mf = 250.4 K, As = 262.2 K, Af = 274.1 K, T C M = 172.0 K, and T C A = 307.3 K. Also, it has been discovered elsewhere [78] that the magnetic transformation temperature of the austenite phase (Curie temperature T C A ) is approximately 325 K for Ni 50 Mn 36 Sn 14 alloys. In the regions of 230 K (Ms)-170 K (Mf) and 195 K (As)-255 K (Af), which correspond to martensitic and reverse martensitic transformations, respectively, dramatic changes in magnetization are seen below T C A .…”

“…Similarly, further authors have estimated that the magnetic transition from ferromagnetic (FM) to paramagnetic (PM) state can occur simultaneously with the structural transformation from austenite (AS) to martensite (MS) [79]. Referring to Sun et al [78], in the Ni 50 Mn 36 Sn 14 Heusler alloy, the temperature at which magnetic transformation occurred was roughly 325 K. In the ranges of 230 K (Ms)-170 K (Mf) and 195 K (As)-255 K (Af), respectively, dramatic changes in magnetization were seen below Curie temperature, which was related to MT and reverse MT. As a further feature, the zero-field cooling (ZFC) curve demonstrated a blocking temperature TB (65 K) inflection point that indicated the presence of magnetically inhomogeneous states.…”

The Tools and Parameters to Consider in the Design of Power Transformer Cooling Systems

“…These losses occur as a result of the alternating magnetic flux in the core. Their sources are magnetic hysteresis [14][15][16][17] and eddy currents [18,19]. Hysteresis losses are proportional to the surface area of the magnetic hysteresis loop in the transformer core.…”

Structure, Microstructure and Magnetocaloric/Thermomagnetic Properties at the Early Sintering of MnFe(P,Si,B) Compounds

“…Setting aside the case of micro-or nanostructured materials which involve specific mechanisms [30][31][32] and going beyond the simple aspect of sample purity or secondary phase content, the sample synthesis technique may exert an extrinsic control on the phase transition and therefore significantly affect the magnetocaloric performances. One of the most typical examples is the great sensitivity of martensitic transitions to microstructural details [33][34][35][36][37][38].…”