In the present work, the influence of W-doping instead of Ni and Sn on the structural and martensitic transformation (MT) characteristics, magnetic behavior and inverse magnetocaloric effect (MCE) exhibited by Ni47Mn40Sn13 metamagnetic shape memory alloys (metaMSMAs) has been investigated. The inverse MCE in the vicinity of MT was measured: (i) by the indirect method using thermomagnetization curves and temperature dependence of heat capacity, and (ii) by the direct measurements of the field-induced adiabatic temperature changes, ΔTad. It is found that both methods revealed ΔTad values which are in a good agreement with each other. The results of direct method show the largest MCE at MT for Ni46W1Mn40Sn13 alloy (the maximum absolute values of 2.2 K for a magnetic field change of 1.96 T) if compared to the other two alloys. The outcomes demonstrate that doping by W is an efficient tool to tailor properties of the Ni–Mn–Sn MCE alloy, which is a promising material for the magnetic refrigeration.

The influence of the W-doping on the martensitic transformation, magnetic properties and exchange bias (EB) effect in the Ni47Mn40Sn13-xWx (x=0, 0.5, 1, 1.25 at.%) magnetic shape memory alloys has been investigated. It is found that the W-doping causes a simultaneous reduction ofboth the ferromagnetic exchange coupling and enhancement of the magnetic anisotropy, leading to a decrease of the magnetic moment of the low-temperature phase and to a higher attainable EB. The magnetic memory measurements reveal the presence of a glassy magnetic ground state, which can significantly impact the reduction of magnetization and enhancement of EB in the studied bulk alloys. It is argued that the glassy magnetic ground state originates from the partial magnetic disorder resulting from the correlation between the antiferromagnetic and ferromagnetic states. The results demonstrate that the doping by W instead of Sn is an efficient tool to tailor the EB effect in the Ni-Mn-Sn-based Heusler alloys, whereby they are promising for spintronic applications.

Martensitic transformation (MT), magnetic properties, and magnetocaloric effect (MCE) in Heusler-type Ni47Mn40Sn13-xCdx (x = 0, 0.75, 1, 1.25 at. %) metamagnetic shape memory alloys (MetaMSMAs) are investigated, both experimentally and theoretically, as a function of doping with Cd. Ab-initio computations reveal that the ferromagnetic (FM) configuration is energetically more favorable in the cubic phase than the antiferromagnetic (AFM) state in undoped and doped alloys as well. Moreover, it is revealed that the alloys in the ground state exhibit a tetragonal structure confirming the existence of MT, in agreement with the experiments. It was indicated, both in theory and practice, that a reduction of the unit cell volume and an increase of the MT temperature as a function of the Cd doping. Indirect estimations of MCE in the vicinity of MT were carried out by using thermomagnetization curves measured under different magnetic fields up to 5 T. The results demonstrated that the doped alloys exhibit enhanced values of the inverse MCE comparable with those of Ni-Mn-based MetaMSMAs. Maximum magnetic entropy change in a field change of 2 T increases from 3.0 for the undoped alloy to 3.4 and 5.0 for the alloys doped with 0.75 and 1 at.% of Cd, respectively. The inverse and conventional MCE were explored by direct measurements of the adiabatic temperature change under the magnetic field change of 1.96 T. The Cd doping increased the maximum of inverse MCE by nearly 78% from 0.9 K to 1.6 K for the undoped and doped alloys, respectively. The results depicted that Cd doping can effectively tailor the structural, magnetic, and MCE properties of the Ni–Mn–Sn MetaMSMAs.

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