Importance of site occupancy and absence of strain glassy phase in Ni2−Fe Mn1.5In0.5

Abstract

Martensitic transition temperature steadily decreases in Ni 2−x Fe x Mn 1.5 In 0.5 and is completely suppressed at x = 0.2. Despite suppression of martensitic transition, Ni 1.8 Fe 0.2 Mn 1.5 In 0.5 does not display the expected strain glassy phase. Instead, a ground state with dominant ferromagnetic interactions is observed. A study of structural and magnetic properties of x = 0.2 reveal that the alloy consists of a major Fe rich cubic phase and a minor Fe deficient monoclinic phase favoring a ferromagnetic ground state. This is exactly opposite of that observed in Ni 2 Mn 1−y Fe y In 0.5 wherein a strain glassy phase is observed for y = 0.1. The change in site symmetry of Fe when doped for Ni in contrast to Mn in the Heusler composition seems to support the growth of the ferromagnetic phase.

Lattice strain accommodation and absence of pre-transition phases in Ni50Mn25+x In25−x

“…It is pertinent to note that with an increase in excess Mn concentration, T CM decreases indicating a weakening of ferromagnetic interactions. In fact, for x = 12.5 alloy T CM is reported to be 39 K [9].…”

“…Nevertheless, several questions remain unanswered for example, do all martensitic alloys doped with defects display a strain glass transition? Recently we have shown that in magnetic Heusler alloys undergoing martensitic transformation, site occupancy of the dopant plays a vital role in determining the alloy ground state [8,9]. In Fe doped Ni-Mn-In alloys, when Mn is replaced by Fe, the suppression of the martensitic phase occurs via a strain glassy phase [8].…”

Strain glass versus antisite disorder induced ferromagnetic state in Fe doped Ni–Mn–In Heusler martensites

“…Figure 1 represents the room temperature x-ray diffraction data analysed by Le Bail method using Jana 2006 software [24]. In the series Ni 2 Mn 1.5 − x Fe x In 0.5 , the alloys with lower Fe concentration (x ≤ 0.1) exhibit 7 M modulated martensitic structure (figures 1(a) and (b)) just like the parent Ni 2 Mn 1.5 In 0.5 [22]. With the increase in Fe content (x = 0.2), there is a structural transition from the martensitic phase to a major L2 1 and a minor impurity phase, as seen in figure 1(c).…”

“…At a critical concentration of x = 0.1, despite the average structure being martensitic, strain glassy phase appears below the glass transition temperature T g = 350 K [16]. On the other hand when Fe is doped to replace Ni, to realize Ni 2 − y Fe y Mn 1.5 In 0.5 , the ferromagnetic interactions are enhanced with a complete suppression of the martensitic state at y = 0.2 [22].…”

Lattice strain accommodation and absence of pre-transition phases in Ni$_{50}$Mn$_{25+x}$In$_{25-x}$

“…In Fe doped Ni-Mn-In alloys, when Mn is replaced by Fe, the suppression of the martensitic phase occurs via a strain glassy phase [8]. On the contrary, when Fe is substituted for Ni, the resulting ground state is a cubic ferromagnet [9].…”