Magnetocaloric Effect in Metamagnetic Shape Memory Alloy

Authors Anna Kosogor1, Serafima I. Palamarchuk2, Victor A. L’vov1,2

1Institute of Magnetism NASU and MESU, 36, Vernadsky Blvd., 03142 Kyiv, Ukraine

2National Taras Shevchenko University, 4G, Glushkov Ave., 03187 Kyiv, Ukraine

Е-mail annakosogor@gmail.coma
Issue Volume 12, Year 2020, Number 1
Dates Received 18 December 2019; revised manuscript received 15 February 2020; published online 25 February 2020
Citation Anna Kosogor, Serafima I. Palamarchuk, Victor A. L’vov, J. Nano- Electron. Phys. 12 No 1, 01018 (2020)
PACS Number(s) 81.30.Kf, 75.30.Sg, 65.40.Ba
Keywords Magnetostructural transition, Specific heat, Adiabatic temperature change, Debye equation.

In the present article, the results of quantitative theoretical analysis of the normal and inverse magnetocaloric effects (MCEs) in metamagnetic shape memory alloy (MMSMA) are reported. Taking into account that the direct experimental evidences of antiferromagnetic ordering were obtained recently, the theoretical analysis was carried out starting from the expression for the magnetic energy of antiferromagnet with two magnetic sublattices. The adiabatic temperature change caused by the inverse and normal MCEs in MMSMA was evaluated and compared with experimental data obtained for Ni2Mn1.4Sn0.6 alloy. The adiabatic temperature change depends on the magnetic-field-induced entropy change and heat capacity of the alloy. To obtain the quantitative agreement between the experimental and theoretical data the magnetic and non-magnetic contributions to the heat capacity of MMSMA were taken into account and evaluated. Due to this, the contribution of spontaneous deformation, which accompanies the magnetostructural phase transition, to the total value of MCE was discovered. The increase of heat capacity caused by the change of magnetic state of the alloy during the phase transition was computed as well. It was shown that the temperature peak of heat capacity, observed in the temperature range of magnetostructural phase transformation of Ni-Mn-Sn alloy, is caused by both spontaneous deformation of the crystal lattice and magnetic ordering of the alloy. It was shown that the presence of the peak of heat capacity diminishes the expected from the Debye equation value of adiabatic temperature change by factor 2.5. To the best of our knowledge, the role of spontaneous deformation of the crystal lattice in the temperature dependence of heat capacity and inverse MCE was not considered until now.

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