Effect of crystallographic alignment on the magnetocaloric effect in alloys near the Ni(sub2)MnGa stoichiometry
A K. Giri, Brigitte A. Paterson, Michael V. McLeod, Cindi L. Dennis, B S. Majumdar, Kyu C. Cho, Robert D. Shull
Prior to the development of commercial applications of magnetic refrigerator technology, a large magnetocaloric effect (MCE) in polycrystalline materials must be realized for relatively low magnetic field changes. In this context, a crystallographic alignment technique, consisting of thermal cycling about the martensite phase transition temperature under a compressive stress, was applied to Heusler alloys with nominal composition Ni2+xMn1-xGa (x = 0.14, 0.16). Magnetic measurements show that the maximum entropy changes of -16 Jkg-1K-1 and -24 Jkg-1K-1 for samples with x=0.14 and 0.16 respectively occurred for a magnetic field change of 7 T. Furthermore, there was a 56-79% enhancement of the maximum magnetic entropy change after grain alignment, for the same magnetic field change of 7 T. This suggests that thermal cycling under compressive stress may either increase grain alignment along the magnetic easy (001) axis, and/or it may enhance the ease with which a magnetic field is later able to grow favorably oriented twin variants that manifests as an increase of magnetization of the material. Therefore, such an alignment technique may be utilized to enhance the MCE of similar Heusler alloys.
, Paterson, B.
, McLeod, M.
, Dennis, C.
, Majumdar, B.
, Cho, K.
and Shull, R.
Effect of crystallographic alignment on the magnetocaloric effect in alloys near the Ni(sub2)MnGa stoichiometry, Applied Physics
(Accessed June 7, 2023)