Investigation of magnetic phase transition and magnetocaloric effect of (Ni,Co)-Mn-Al melt-spun ribbons

¹ Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Ha Noi, Viet Nam
² Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Ha Noi, Viet Nam
³ Faculty of Physics, Hanoi Pedagogical University 2, 32 Nguyen Van Linh, Vinh Phuc, Vietnam
⁴ Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Ha Noi, Viet Nam
⁵ Kotelnikov Institute of Radio-engineering and Electronics of RAS, Moscow, Russia
⁶ Department of Physics, Chungbuk National University, Cheongju 361 - 763, South Korea

^* Corresponding author: yennh@ims.vast.ac.vn

Published online: 4 July 2018

Abstract

Magnetic phase transition, magnetocaloric effect and critical parameters of Ni_50-xCo_xMn_50-yAl_y (x = 5 and 10; y = 17, 18 and 19) rapidly quenched ribbons have been studied. X-ray diffraction patterns exhibit a coexistence of the L2₁ and 10M crystalline phases of the ribbons. Magnetization measurements show that all the samples behave as soft magnetic materials with a low coercive force less than 60 Oe. The shape of thermomagnetization curves considerably depends on Co and Al concentrations. The Curie temperature (T_C) of the alloy ribbons strongly increases with increasing the Co concentration and slightly decreases with increasing the Al concentration. The Ni₄₅Co₅Mn₃₁Al₁₉ and Ni₄₀Co₁₀Mn₃₃Al₁₇ ribbons reveal both the positive and negative magnetocaloric effects. Under magnetic field change (ΔGH) of 13.5 kOe, the maximum magnetic entropy change (|ΔS_m|_max) of the Ni₄₅Co₅Mn₃₁Al₁₉ ribbon is about 2 and -1 J·kg⁻¹·K⁻¹ for negative and positive magnetocaloric effects, respectively. Basing on Arrott - Noakes and Kouvel - Fisher methods, critical parameters of the Ni₄₅Co₅Mn₃₁Al₁₉ ribbon were determined to be T_C ≈ 290 K, β ≈ 0.58, γ ≈ 0.92 and δ ≈ 2.59. The obtained values of the critical exponents indicate that the magnetic order of the alloy ribbon is close to the mean-field model.