Influence of chemical pressure in Sn-substituted Ni2MnGa Heusler alloy: Experimental and theoretical studies

Abstract

The influence of the chemical pressure on the magneto-structural properties of the Ni2MnGa Heusler alloy after a gradual substitution of Ga by Sn atoms was theoretical and experimentally studied in this work. Our data clearly show that an expansion of the L21-cell volume due Sn-substitution causes a diminution of the internal structural stress and favors the austenitic state in low temperatures where martensitic phase should prevail. It is also shown that the total magnetization reduces with increasing Sn-content, a behavior explained by a reduction of the Ni-magnetic moment, since an increase of Mn-magnetic moment was theoretically calculated. The Sn-substitution effect in the Ni2MnGa compound is similar to that found in experiments performed under high applied magnetic fields, which means that in both cases there is an increase of the L21 cell-volume favoring the austenitic state in low temperatures. Magnetization values in martensitic state of the pure Ga-compound systematically reduce after consecutive M(T) thermal cycle recorded at 5 mT; an effect not yet reported within our knowledge and attributed here to modifications in local magnetic anisotropies during the field cycles.

Influence of W doping on the structure, magnetism and exchange bias in Ni47Mn40Sn13− x W x Heusler alloys

“…As the W content increases, the MT temperature is continuously growing. This behavior can be explained by the rise of electron concentration (e/a) and by a gradual decrease in the unit cell volume induced by the W-doping (see table 1) [18]. The DSC measurement for the x = 1.25 sample confirms the presence of the martensitic phase at room temperature, which is in line with the XRD results.…”

Martensitic transformation, magnetic entropy, and adiabatic temperature changes in bulk and ribbon Ni48Mn39.5Sn12.5−xInx (x = 2, 4, 6) metamagnetic shape memory alloys

“…It is given by the Zeeman energy E = µ 0 ΔM•H [32][33][34][35]. Since, the magnetic moment in such alloys is mainly attributed to the Mn atoms, coupled via the oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions [36], the magnetic properties and magnetic ordering temperatures are sensitive to the d Mn -d Mn distance [37,38].…”

The effect of Pd on martensitic transformation and magnetic properties for Ni50Mn38−xPdxSn12Heusler alloys

“…The FIG. 2 12 , which corresponds to the increase of e/a from 8.26 to 8.32. Obviously, the variation tendency of the phase transformation could not follow the fact that M s monotonically increases with the increase of e/a, and vice versa.…”

“…As a result, the abundant properties during the MPT would be expected. In this paper, we focus on the influence of Pd doping on the MPT and magnetic properties for Ni 50 Mn 38−x Pd x Sn 12 Heusler alloys with x = 0, 2, 4 and 6. At the same time, both the shape memory effect and magnetocaloric effect of Ni 50 Mn 34 Pd 4 Sn 12 have been investigated during the MPT, respectively.…”

“…Generally speaking, the most outstanding properties of these alloys are relevant to the martensitic phase transition (MPT) during which the high temperature cubic L2 1 phase (austenite) with a higher symmetry transforms to a low temperature phase (martensite) with a lower symmetry (tetragonal, orthorhombic, or monoclinic phase). 9,10 The mechanism behind these effects can be ascribed to the valence electron concentration (e/a), 1 bond length between constructive elements (or chemical pressure) 11,12 or the contribution of hybridization. 13,14 Both the MPT and magnetic properties are very sensitive to their compositions, especially doped with 3d transition elements on Ni or Mn site.…”