Effect of Si Doping on Magnetic and Magnetocaloric Properties of Ni–Co–Mn–Sn Alloys

Abstract

Herein, the magnetic, exchange bias (EB), and magnetocaloric properties of polycrystalline Ni ₄₈ Co _1.5 Mn ₃₅ Sn _15.5-x Si _x (x=1, 2, and 4) Heusler alloys have been investigated by magnetic measurements. All these alloys are found to undergo a first-order structural phase transition from martensite to austenite along with a second-order ferromagnetic to paramagnetic transition. It is observed that martensitic transition temperature shifts to lower temperature with increasing Si substitution in place of Sn, whereas the Curie temperature is insensitive to the doping amount. Magnetic entropy change (ΔS _M ) and net relative cooling power are measured across martensite to austenite transition and the corresponding values are found to 10.86, 5.46, 2.42 Jkg ^-1 K ^-1 and 122.7, 144.5, and 63 Jkg ^-1 for x=1, 2, and 4 alloys due to a field change of 50 kOe, respectively. Interestingly, with increasing Si substitution in place of Sn, hysteresis loss reduces significantly from 52.1 J/kg (x=1) to 8.62 J/kg (x=4). However, the EB property of these alloys does not change significantly due to the doping amount.