Direct and Inverse Magnetocaloric Effect in a Ni50Mn35Al2Sn13 Heusler-Alloy Ribbon Sample

Abstract

The magnetization of a fast-hardened ribbon Ni50Mn35Al2Sn13 sample has been studied and its magnetocaloric effect (MCE) has been directly measured in the temperature range 100–350 K. The MCE has been investigated in a cyclic magnetic field of 1.8 T strength at a frequency of 0.2 Hz. The value of the inverse effect near the temperature of the magnetostructural phase transition (MSPT) has been shown to depend on the rate of temperature scanning. The higher the scanning rate, the greater the MCE value due to the kinetic relaxation effect in the martensitic phase and the irreversibility of the phase transition in the magnetic fields used. The value of the inverse effect when the magnetic field is turned on once is –0.39 K in the field of 18 kOe, and the value of the direct effect is 0.2 K. The significant magnetization increase observed near the ТС in a weak magnetic field (100 Oe) has been attributed to both the Hopkinson effect and the coexistence of two crystalline phases (austenite–martensite).