Direct and indirect measurement of the magnetocaloric effect in bulk and nanostructured Ni-Mn-In Heusler alloy

Mohammadreza Ghahremani,Marjan Hosseinnia,Amir Aslani,Edward Della Torre,Lawrence H Bennett

doi:10.1063/1.5007223

Mohammadreza Ghahremani, Marjan Hosseinnia + Show 3 more

Open Access

https://doi.org/10.1063/1.5007223

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Abstract

A systematic study of the magnetocaloric effect of a Ni51Mn33.4In15.6 Heusler alloy converted to nanoparticles via high energy ball-milling technique in the temperature range of 270 to 310 K has been performed. The properties of the particles were characterized by x-ray diffraction, electron microscopy, and magnetometer techniques. Isothermal magnetic field variation of magnetization exhibits field hysteresis in bulk Ni51Mn33.4In15.6 alloy across the martensitic transition which significantly lessened in the nanoparticles. The magnetocaloric effects of the bulk and nanoparticle samples were measured both with direct method, through our state of the art direct test bed apparatus with controllability over the applied fields and temperatures, as well as an indirect method through Maxwell and thermodynamic equations. In direct measurements, nanoparticle sample’s critical temperature decreased by 6 K, but its magnetocaloric effect enhanced by 17% over the bulk counterpart. Additionally, when comparing the direct and indirect magnetocaloric curves, the direct method showed 14% less adiabatic temperature change in the bulk and 5% less adiabatic temperature change in the nanostructured sample.

Highlights

With the growing concern about global warming and energy resources scarcity, environmentally friendly magnetic refrigeration technology is a promising alternative to replace low-efficient conventional cooling technology which works based on vapor compression cycle of harmful gasses such as Freon
The discrepancy here between the direct and indirect measurements is related to the heat losses in direct method which can be lessened by better sample isolation and improving thermal contact between nanostructured powder and thermal sensor which must have a negligible thermal mass in comparison with the nanopowders
Ni51Mn33.4In15.6 Heusler alloy nanoparticles were successfully synthesized through high energy ball milling technique

Summary

INTRODUCTION

As a result rare-earth-free refrigerant materials, in particular Heusler alloys are a promising candidate because of the fairly low-cost of the material and their large value of MCE as an outcome of martensitic phase transformation that takes place in a magnetically ordered state.[7] Heusler alloys have been studied because of their several technological implications and multifunctional properties[8] leading to a variety of research such as magnetoresistive behavior,[9,10] magnetic shape memory effect,[11,12] barocaloric effect,[13] magnetocaloric effect,[14,15] etc. Increasing the RCP increases the amount of refrigeration obtainable from the particular refrigerant and field excursion, and tends to increase the thermodynamic efficiency of the cycle.[6,30] Improvement in the RCP mainly relies on broadening the magnetic entropy change by either coupling two phases of magnetic materials with desirable properties or nanostructure synthesis with the main motivation rooted in their inherent tendency to have distributed exchange coupling, which will broaden the magnetic entropy curve.[2,31] These have motivated us to study the direct and indirect MCE measurements in the bulk and nanostructured Ni51Mn33.4In15.6 Heusler alloy

EXPERIMENTAL

RESULTS AND DISCUSSIONS

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CONCLUSIONS