Influence of Al on structure, magnetic properties and magnetocaloric effect of Ni50Mn37−xAlxSn13 ribbons

Hai Yen Nguyen, Thi Mai Nguyen, Manh Quang Vu, Thi Thanh Pham, Dang Thanh Tran, Huu Duc Nguyen, Le Thi Nguyen, Hoang Ha Nguyen, Victor Koledov, Alexander Kamantsev, Alexey Mashirov and Huy Dan Nguyen

Abstract

Influence of Al-concentration on structure, magnetic properties and magnetocaloric effect of Ni₅₀Mn_37−xAl_xSn₁₃ (x = 2, 4, 6 and 8) rapidly quenched ribbons was investigated. X-ray diffraction analysis shows that the ribbons exhibit single phase with a L₂₁-cubic structure. Curie temperature, T_C, of the alloy is slightly increased with increasing Al-concentration. Specially, the sample with x = 2 has both the first- (FOPT) and second- (SOPT) order magnetic phase transitions. The reason for the FOPT in the alloy ribbons is due to existence of the structural transformation between martensitic and austenitic phases. The Ni₅₀Mn₃₅Al₂Sn₁₃ alloy owns both the positive and negative magnetocaloric effects with maximum magnetic entropy changes of -0.8 and 2.6 J.kg^-1.K^-1 (in magnetic field change ΔH = 12 kOe), respectively. By using Arrott-Noakes and Kouvel-Fisher methods, the critical parameters of the alloy were determined to be close to those of the mean field theory of long-range ferromagnetic orders