Magnetic properties, martensitic and magnetostructural transformations of ferromagnetic Ni–Mn–Sn–Cu shape memory alloys

Abstract

The influence of Cu doping on structural and magnetic properties of Ni50-xMn36Sn14-yCux, y (x=0, 1,2 and y=1 at. %) ribbons has been investigated. The crystalline structures of the alloys were resolute by X-ray diffraction (XRD). It is found that the addition of Cu for Ni stabilizes austenite phase, whereas, replacing small amount of Cu for Sn stabilizes modulated martensite phase. Differential scanning calorimetry measurements have proved the characteristic transformation temperatures. The transformation temperatures generally rise as increasing the Cu content. Therefore, the magneto structural transition, analysed by vibrating sample magnetometry, is tuned by appropriate Cu doping in the alloys. Likewise, both martensitic and austenitic states exhibit ferromagnetic behaviour.

Martensitic Transformation, Thermal Analysis and Magnetocaloric Properties of Ni-Mn-Sn-Pd Alloys

“…By this melt spinning technique, ribbon-flake samples were obtained. Additional information about processing and analysis can be found in references [3,4,11].…”

“…Likewise, the addition of a fourth element to Ni-Mn-Sn systems is a current strategy to tune the structural-magnetic transformations and the magnetic behaviour of SMAs, enhancing the properties even though it can also modify the structure [10]. Numerous quaternary systems have been established, such as those with the addition of Cu [11], Co [12], Fe [13], W [14] or Pd [15]. The additions usually produce a shift of the transformation temperatures.…”

“…A parameter has been defined that influences MT temperatures-e/a (average outer electron concentration per atom) [16], which offers a suitable way to control the transition temperature. Likewise, the stoichiometry Heusler structure is X 50 Y 25 Z 25 (also described as X 2 YZ) and some articles analyse the influence on the characteristic temperatures and magnetic response of the addition of a fourth element taking into account the expected site position of this additional element, usually X or Z sites [11,15].…”

Influence of the Cu substitution on magnetic properties of Ni–Mn–Sn–B shape memory ribbons

“…An applied magnetic field leads to stabilization of the high-temperature austenite phase. 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]. A large entropy change and a good magnetocaloric effect occur due to the large magnetization change.…”

“…In order to shift the T M temperatures and to reduce the degree of hysteresis associated with the structural martensitic transition, some elements, such as Co, Cu and Pd, have been substituted/doped to the off-stoichiometric Ni-Mn-Sn system [9,[19][20][21]. It was found that Cu substitution has significant effects on the properties of the Ni-Mn-Sn system; the Cu substitution for Mn and Sn caused a shift of the martensitic transition to high temperatures [7,9,22,23], while the transition with the Cu substitution for Ni shifted to low temperatures [24,25]. Since Cu is non-magnetic, the exchange interactions in the system reduce and thus Curie temperature shifts to low temperatures.…”