Magnetocaloric effect in Ni–Fe–Mn–Sn microwires with nano-sized γ precipitates

• Published in: Applied physics letters 2020-02, Vol.116 (6)
• Main Authors: Zhang, Hehe, Zhang, Xuexi, Qian, Mingfang, Yin, Limeng, Wei, Longsha, Xing, Dawei, Sun, Jianfei, Geng, Lin
• Format: Article
• Language: English
• Subjects: Annealing; Applied physics; Chemical precipitation; Demagnetization; Entropy; High temperature; Iron; Magnetic cooling; Magnetic properties; Magnetic transitions; Manganese; Martensite; Martensitic transformations; Mechanical properties; Nickel; Precipitates
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5132767

Ni45.6Fe3.6Mn38.4Sn12.4 microwires, with nanoscale γ-phase precipitates that enhance the magnetocaloric effects (MCEs) and mechanical properties, were prepared by a melt-extraction technique and subsequent high temperature annealing. The atomic ordering degree significantly increased after annealing, leading to a considerable increment in the structural entropy change (ΔStr) from 4.5 J/kg·K in the as-extracted microwire to 26.6 J/kg·K in the annealed one, and the magnetization difference (ΔM) from 35 A·m2/kg to 51 A·m2/kg under a magnetic field of 5.0 T. Consequently, a positive magnetic entropy change (ΔSM) peak of 15.2 J/kg·K with working temperature span (ΔTFWHM) of 12 K for the first-order martensite transformation followed by a negative ΔSM peak of −4.3 J/kg·K with ΔTFWHM = 50 K for the second-order magnetic transition under μ0ΔH = 5.0 T was achieved. By employing both magnetizing and demagnetizing processes for magnetic cooling, the two successive inverse and conventional MCEs in Ni–Fe–Mn–Sn microwires may show potential applications for micro-devices and systems.