Hysteresis loss reduction and magnetocaloric effect improvement in the Ni-Co-Mn-In alloys

Mohammadreza Ghahremani,Lawrence H Bennett,Amir Aslani,Marjan Hosseinnia

doi:10.1063/1.5130440

Abstract

In this work the magnetocaloric effect (MCE) and hysteresis losses of Ni45Co5Mn(37-x)In(13+x) alloy (x= 0, 0.4) are studied. Also we propose a new approach in calculating the average entropy change to eliminate the overestimation of the magnetic entropy change calculation using Maxwell’s relations which is commonly seen in the indirect MCE calculation in the literature. The attributes of magnetostructural coupling have an important role in the magnetic behavior of these magnetofunctional alloys. This work exhibits that a strong magnetostructural coupling can be achieved over a wide temperature range in this alloy family which results in a higher MCE and relative cooling power (RCP) compared to other Ni-Mn-In based Heusler alloys. It’s shown that by increasing the applied field the peak of the entropy change curves shifts to lower temperatures. Additionally, a small variation in the stoichiometry composition broadens the magnetic entropy change curve and shifts the critical temperatures by about 36 K to around room temperature. Furthermore, due to the enhancement in ferromagnetic exchange interactions in austenite, the magnetization change accompanying the martensitic transformation is greatly improved, resulting in a large magnetic entropy change of 31 Jkg-1K-1 under 5T field. The broadened and higher peak of the entropy change curves produced a significantly high relative cooling power in Ni45Co5Mn36.6In13.4 (488 JKg-1) and Ni45Co5Mn37In13 (317 JKg-1) under 5T field. These results are especially promising in finding low-cost, high-performance magnetocaloric material for magnetic refrigeration systems.

Highlights

Magnetic refrigeration is an environmentally friendly cooling technology and a viable candidate to replace the conventional cooling technology which works based oncompression of harmful gases.1–3 Magnetic refrigeration exploits magnetocaloric effect (MCE), an intrinsic property of a magnetic material.4 For the development of roomtemperature magnetic refrigerators, synthesizing magnetocaloric materials with the following characteristics are essential: (1) the critical transition temperature should be around room temperature; (2) it should produce a high MCE per unit of applied magnetic field with sufficiently wide operating temperature range; (3) have negligible hysteresis losses; (4) be inexpensive to become commercially feasible
This work exhibits that a strong magnetostructural coupling can be achieved over a wide temperature range in this alloy family which results in a higher MCE and relative cooling power (RCP) compared to other Ni-Mn-In based Heusler alloys
The results show several significant features: (i) A minor change in the stoichiometry of Ni45Co5Mn(37-x)In(13+x) shifted the Curie temperature by 36K to around room temperature. (ii) Increasing the magnetic field would shift the entropy change curve to the lower temperatures. (iii) Enhancement in ferromagnetic exchange interactions resulted in a large magnetic entropy change of 31 Jkg-1K-1 under 5T which was superior to the values reported for other Ni-Mn rich alloys in literature. (iv) The larger exchange couplings and the higher magnetization change broadened the entropy change curves of the samples. (v) The higher peak value and broadened entropy change resulted in a higher relative cooling power in Ni45Co5Mn36.6In13.4 (488 JKg-1) and Ni45Co5Mn37In13 (317 JKg-1) under 5T field

Summary

INTRODUCTION

Magnetic refrigeration is an environmentally friendly cooling technology and a viable candidate to replace the conventional cooling technology which works based on (de)compression of harmful gases. Magnetic refrigeration exploits MCE, an intrinsic property of a magnetic material. For the development of roomtemperature magnetic refrigerators, synthesizing magnetocaloric materials (refrigerant) with the following characteristics are essential: (1) the critical transition temperature should be around room temperature; (2) it should produce a high MCE per unit of applied magnetic field with sufficiently wide operating temperature range; (3) have negligible hysteresis losses; (4) be inexpensive to become commercially feasible. Ni-Mn-In can affect the martensitic and magnetic transformation temperatures and enhances the ferromagnetic properties of the parent austenitic phase.. MCE can be obtained directly by varying the field and measuring the temperature change of a refrigerant. An indirect method measurement is often used which provides ΔTad via Maxwell’s equations and the thermodynamic analysis of the temperature and field-dependent magnetization measurements.. The use of Maxwell’s equations to describe the magnetic entropy change (ΔSM) in materials that have a first-order phase transition has been questioned as they are accompanied by hysteresis loses.. The use of Maxwell’s equations to describe the magnetic entropy change (ΔSM) in materials that have a first-order phase transition has been questioned as they are accompanied by hysteresis loses.32,33 Though, this artifact can be minimized after using appropriate protocol for the measurements.. Direct measurements are desirable as they provide ΔTad without extensive data processing but are somehow challenging. As a result, an indirect method measurement is often used which provides ΔTad via Maxwell’s equations and the thermodynamic analysis of the temperature and field-dependent magnetization measurements. The use of Maxwell’s equations to describe the magnetic entropy change (ΔSM) in materials that have a first-order phase transition has been questioned as they are accompanied by hysteresis loses. Though, this artifact can be minimized after using appropriate protocol for the measurements. in this work we propose a new approach to eliminate the overestimation error incorporated in the indirect MCE measurement

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSIONS