Two successive magneto-structural transformations and their relation to enhanced magnetocaloric effect for Ni55.8Mn18.1Ga26.1 Heusler alloy

Abstract

In the present work, two successive magneto-structural transformations (MSTs) consisting of martensitic and intermartensitic transitions have been observed in polycrystalline Ni55.8Mn18.1Ga26.1 Heusler alloy. Benefiting from the additional latent heat contributed from intermediate phase, this alloy exhibits a large transition entropy change ΔStr with the value of ~27 J/kg K. Moreover, the magnetocaloric effect (MCE) has been also evaluated in terms of Maxwell relation. For a magnetic field change of 30 kOe, it was found that the calculated value of refrigeration capacity in Ni55.8Mn18.1Ga26.1 attains to ~72 J/kg around room temperature, which significantly surpasses those obtained for many Ni-Mn based Heusler alloys in the same condition. Such an enhanced MCE can be ascribed to the fact that the isothermal entropy change ΔST is spread over a relatively wide temperature interval owing to existence of two successive MSTs for studied sample.

Enhanced magnetocaloric effect in Ni-Mn-Sn-Co alloys with two successive magnetostructural transformations

“…4b), indicating that an incomplete MT with residual austenite even at 173 K. This phenomenon is consistent with some other Ni-Mn-based alloys 52,53 , implying that the complete MT might be difficult to be achieved supposing that slightly inhomogeneous composition distribution exists in the bulk alloy. Furthermore, the two successive magnetostructural transition processes (A → 10 M and A → 10 M + 6 M) in the present alloy are essentially different from the two successive martensite (MT) and intermartensite transition (IMT) occur in some other types of FMSMAs such as Ni 55.8 Mn 18.1 Ga 26.1 40 , Ni 50 Mn 34 In 12 Sb 4 54 and Ni 49−x Cu x Mn 38 Sn 13 (0.5 < x < 2) 55 alloys.

Figure 4 In-situ X-ray diffraction (XRD) patterns for Co6 alloy in the range 35° < 2θ < 50° during cooling ( a ) from 343 K to 283 K and ( b ) from 273 K to 173 K, respectively. The diffraction peaks marked by five-pointed star corresponds to the sample stage.

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“…The enhancement of ΔM favors the magnetic entropy change ΔS M according to the Maxwell equation and broadens the ΔT FWHM due to the increase in Zeeman energy 45 . Furthermore, the percentage of MT caused by field-induced metamagnetic transition mainly relies on d T M /d H 40 ( T M denotes the MT equilibrium temperature, as shown in Fig. 3, which can be assessed by the Clausius-Clapeyron magnetic equation − d T M /dH  =  ΔM/ΔS tr .…”

“…For example, rare earth containing low temperature magnetic refrigeration compounds, such as TbMn 2 Si 2 36 , ErGa 37 , DyB 2 38 , HoPdIn 39 , may exhibit a two successive magnetic transitions behavior deriving from the coupling of spin-reorientation temperature (TSR) and Curie temperature ( T c ); Two successive ΔS M peaks with the same sign, associated with a first-order martensite transformation (MT) and an intermediate martensite transformation (IMT), have also been discovered in some Ni-Mn-X alloys after composition tuning or under external pressure 40–42 . These two adjacent transformations lead to a partially overlap of the refrigerant temperature intervals, yielding an improved refrigerating capacity.…”

Magnetocaloric Properties of Fe-Ni-Cr Nanoparticles for Active Cooling

“…Energy efficient magnetocaloric materials for magnetic cooling have attracted intense research interest due to unsustainable energy consumption and limitations of current cooling technology123456789. A well-known milestone in magnetic cooling is the development of a compressor free wine cooler based on magnetic cooling, developed by Haier, BASF and Astronautics corporation1011.…”

Review of magnetic properties and magnetocaloric effect in the intermetallic compounds of rare earth with low boiling point metals

“…Second is that Pecharsky and Gschneider [10] observed a giant MCE in the Gd 5 (Si 2 Ge 2 ) compound. Besides the discovery of the giant MCE in Gd 5 (Si 2 Ge 2 ) and related compounds, [10,11] a number of materials with giant/large MCE have been realized in last three decades, for example RECo 2 (RE = Er, Ho, and Dy) alloys, [12,13] MnAs based compounds, [14][15][16][17] manganites (RE,M)MnO 3 , (RE = lanthanide, M = Ca, Sr, and Ba), [18,19] Ni-Mn-X (X = Ga, In, and Sn) based Heusler alloys, [20][21][22][23][24] La(Fe,Si) 13 and related compounds, [25][26][27][28] MnTX (T = Co, Ni, and Fe; X = Si, Ge) based compounds [29][30][31][32] as well as some rare earth (RE) based intermetallic compounds. [33][34][35][36] The structure, physical properties as well as the MCE and its application in most of the above mentioned materials have been summarized in a number of reviews articles [11-14, 17-19, 22, 23, 26, 27, 32-35, 37-40] which will not be repeated here.…”