Magnetic studies of Fe-doped martensitic Ni₂Mn_1.44Sn_0.56-type Heusler alloy

Abstract

Localization and magnetism of Fe replacing either Mn or Ni in the Ni2Mn1.44Sn0.56-type Heusler alloy have been systematically investigated using magnetization, scanning electron microscopy and Mössbauer spectroscopy. It has been shown that the addition of Fe either in Mn or in Ni sites reduces the fraction of the Mn-rich NiMnSn-type Heusler alloys that has short-range antiferromagnetic interactions; consequently it reduces the martensitic–austenitic transition temperature and increases the thermal hysteresis width due to an increase in atomic disorder caused by Fe replacements. The Fe atoms in Mn sites have two magnetic configurations with magnetic moments of 0.8μB/Fe and 1.4μB/Fe in the martensitic orthorhombic structure, while Fe in Ni sites have magnetic moments smaller than 0.1μB/Fe. These results indicate that the Fe atoms are distinctly substituting either Mn or Ni and the decrease in the martensitic phase transition temperature for increasing Fe content can be mainly attributed to the Fe atoms in the Mn sites in both cases.

The influence of chemical disorder enhancement on the martensitic transformation of the Ni50Mn36Sn14 Heusler-type alloy

“…A Shimadzu SSX 550 scanning electron microscope (SEM) was used to confirm the phase formation and its composition, using the energy dispersive X-ray spectroscopy (EDX), from polished flat pieces obtained from the central part of the annealed pellets. As we previously reported for other set of samples similarly prepared [20,21], more than 99% of the SEM image areas can be associated with a single phase corresponding to the L21-B2-type structure in accord with the X-ray diffraction result. These EDX results confirm that the nominal compositions indeed correspond to the planned alloys.…”

“…Field cooled (FC) and field heated (FH) magnetization versus temperature [M(T)] curves were recorded between 70 and 320 K using a commercial physical property measurement system (Quantum Design PPMS) coupled to an Evercool model cryostat and under an applied DC magnetic field up to 50 kOe. These curves were obtained using protocols described elsewhere [21]. As previously reported, any thermal hysteresis observed between FC and FH M(T) curves can directly be associated with the first-order character of the martensitic phase transition (MPT).…”

“…Particularly, in the Ni 50 Mn 36 Sn 14 (or simply Ni 2 Mn 1.44 Sn 0.56 ) Heusler-type alloy, the martensitic transition temperature (T M ) value is about 220 K [15,20,21,23]. Above that, a ferromagnetic (FM) austenitic state is stable and the cubic crystal structure has a lattice parameter a ≈ 6Å [15].…”

Distribution of Transition Temperatures in Magnetic Transformations: Sources, Effects and Procedures to Extract Information from Experimental Data

“…However, the crystal structure of these compounds strongly depends on the composition and the quenching rate, which can produce site disorder and will drastically influence the magnetic properties due to the ferromagnetic/antiferromagnetic exchange interaction between atoms on the martensitic transformation. In this sense, Passamani et al [64] reported that Ni 2-x Fe x Mn 1.44 Sn 0.56 alloys show a drastic shift of the martensitic transformation after the replacement of Fe atoms for Ni and/or Mn. In this case, Fe-Mn ferromagnetic interactions compensate Mn-Mn antiferromagnetic ones, which leads to the stabilization of austenite phase.…”

DecipheringM–Tdiagram of shape memory Heusler alloys: reentrance, plateau and beyond

“…Further details about preparation and characterization of our samples can be found elsewhere [10]. ZFC and FC measurements of magnetization as a function of temperature M (T ) and magnetic field M (H) were performed using a Quantum Design-MPMS-5 SQUID magnetometer working in the temperature range from 2 to 400K and the field range from 0 to 50kOe [10]. $ %& the second order phase transitions.…”