Abstract
The Heusler alloy Ni50-xCuxMn38Sn12 + By (x = 0, 1, 3 and 5) was successfully produced in ribbon form using melt spinning technique. The magnetic properties of the obtained ribbons were analyzed in detail. In all ribbons, it was detected that the ferromagnetic austenite phase transformed into the weak magnetic martensite phase. A separation between FC and ZFC curves at lower temperatures was found. An increase in the magnetization in FC mode can be attributed to the coexistence of ferromagnetic (FM)/antiferromagnetic (AFM) at martensitic phase. It was found that the transition temperatures shifted to low temperatures with increasing the Cu content. The magnetization results under high magnetic field (10 kOe and 50 kOe) showed a thermal hysteresis between the cooling and heating cycles, which is clear evidence for a first-order transformation in the ribbons. From M–H data, all the ribbons exhibited ferromagnetic behavior at low temperatures below the martensitic transition temperature and paramagnetic behavior at high temperatures above the transition temperature. The results provide us a comprehensive view to reveal the effect of the Cu substitution on the magnetic properties of Ni–Mn-based shape memory ribbons.
Highlights
The shape memory Heusler alloys are of great interest due to good magneto-functional properties such as magnetocaloric effect (MCE) [1, 2], barocaloric effect [3], elastocaloric effect [4], magnetic field-induced shape recovery magnetostrain effect [5], giant magnetoresistance effect [6, 7] and kinetic arrest [8], which rely on magnetic and structural phase transition occurred at the same temperature
Difference between Zeeman energy of austenite phase and that of martensite phase causes a large change in magnetization during the martensitic transition which is evidence of a field-induced martensitic transformation (FIMT) [9]
Shift of the martensitic transformation temperatures to low temperatures with the element substitution/doping to the Ni–Mn–Sn-based shape memory alloys arises from the variation of the valence electron concentration per atom, e/a, or the formation of the second phase, or the change of Mn–Mn distance [44, 45]. e/a was calculated to be 7.99, 8.00, 8.01 and 8.03 for RS, RS1, RS3 and RS5 ribbons, respectively
Summary
The shape memory Heusler alloys are of great interest due to good magneto-functional properties such as magnetocaloric effect (MCE) [1, 2], barocaloric effect [3], elastocaloric effect [4], magnetic field-induced shape recovery magnetostrain effect [5], giant magnetoresistance effect [6, 7] and kinetic arrest [8], which rely on magnetic and structural phase transition occurred at the same temperature. The most commonly used method to tune the TM temperature is to change the composition stoichiometry and to substitute/dope various elements to the host material. Ni–Mn–X (X = In, Sn or Sb)-based alloys are the ideal materials to investigate the magnetic field-induced martensitic transition (MFIMT) properties and possible technological applications such as actuators and sensors. Ni–Mn–X-based alloys undergo a first-order phase transition from a cubic austenite phase with high symmetry to a martensite phase with lower symmetry. It has been found that the change of stoichiometry and the doping of various elements modify the TM temperature and the magnetostructural properties of the alloys, which is essential for technological applications.
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