Measurement independent magnetocaloric effect in Mn-rich Mn-Fe-Ni-Sn(Sb/In) Heusler alloys

TL;DR

This study investigates the magneto-structural transition and magnetocaloric properties of Mn-rich Mn-Fe-Ni-Sn(Sb/In) Heusler alloys, revealing a proportional relationship between transition temperature and valence electron concentration, and demonstrating consistent cooling power despite measurement variations.

Contribution

It provides a systematic analysis of the magneto-structural transition in Mn-rich Heusler alloys with fixed valence electron concentration, highlighting the invariance of cooling power and detailed magnetic entropy change measurements.

Findings

Magneto-structural transition temperature scales with e/a ratio.

Magnetic entropy change curves are broad and consistent across methods.

Cooling power remains invariant (~140 Jkg-1) despite measurement differences.

Abstract

We report a systematic study on the magneto-structural transition in Mn-rich Fe-doped Mn-Fe-Ni-Sn(Sb/In) Heusler alloys by keeping the total valence electron concentration (e/a ratio) fixed. The martensitic transition (MT) temperature is found to shift by following a proportional relationship with the e/a ratio of the magnetic elements alone. The magnetic entropy change across MT for a selected sample (Mn49FeNi40Sn9In) has been estimated from three different measurement methods (isofield magnetization (M) vs temperature (T), isothermal M vs field (H) and heat capacity (HC) vs T). We observed that though the peak value of magnetic entropy change changes with the measurement methods, the broadened shape of the magnetic entropy change vs T curves and the corresponding cooling power (~140 Jkg-1) remains invariant. The equivalent adiabatic temperature change ~ -2.6 K has been obtained from indirect measurements of temperature change. Moreover, an exchange bias field ~ 783 Oe at 5 K and a magnetoresistance of -30% are also obtained in one of these materials.