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

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 (ΔS M ) across MT for a selected sample (Mn 49 FeNi 40 Sn 9 In) 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 ΔS M changes with the measurement methods, the broadened shape of the ΔS M -T curves and the corresponding cooling power (~140 Jkg -1 ) remains invariant. The equivalent adiabatic temperature change (ΔT) ~ -2.6 K has been obtained from indirect measurements of ΔT. Moreover, an exchange bias field ~ 783 Oe at 5 K and a magnetoresistance of -30% are also obtained in one of these materials.

Improved crystallographic compatibility and magnetocaloric reversibility in Pt substituted Ni2Mn1.4In0.6 magnetic shape memory Heusler alloy

“…For loop measurement protocol the sample was heated up to 400 K to ensure the full austenite phase followed by cooling without application of the magnetic field down to 200 K to ensure the complete martensite phase transition and then subsequently sample was heated up to the desired measurement temperature where the M (H) data were recorded ( figure 4(b)) [41,48,70,76]. Using these M (H) curves, ΔSiso is calculated using Maxwell's equation.…”

“…The second method is known as the "indirect measurement method" where ΔSiso is measured using the magnetic hysteresis loop. For the indirect measurement of MCE different measurement protocols have been suggested for the calculation of the ΔSiso especially for the FOMT/FOMST [20,27,48,50,[69][70][71][72][73][74][75]. These measurement protocols are not only used to comment on the correct value of ΔSiso but also useful to comment on the reversibility/irreversibility of MCE [33,49].…”

Computation-Guided Design of Ni–Mn–Sn Ferromagnetic Shape Memory Alloy with Giant Magnetocaloric Effect and Excellent Mechanical Properties and High Working Temperature via Multielement Doping

“…Maximum magnetic entropy changes Δ S peak as a function of temperature and magnetic field for Ni 40 Co 8 Mn 37 Sn 9 Cu 6 alloy (a) and the values of Δ S peak as a function of the corresponding temperature in the magnetic field changes of 1, 2, 5, and 7 T for the prevailing MCE materials such as Ni–Mn-based alloy, LaFeSi, Gd–Si–Ge, and so on (b). − ,,,− ,,,, The data are taken from the present work and the literature (see Supporting Information Note 1 for details).…”

“…Ni–Mn–Sn ferromagnetic shape memory alloys (FSMAs) capable of a direct magnetic field-induced reverse martensitic transformation (MFIRMT) and excellent magnetocaloric effects have promise for application in high-efficiency solid-state refrigeration. − The strong magnetostructural coupling under the martensitic transformation (MT) would lead to a drastic difference of magnetization (Δ M ), which directly affects the MCE. Moreover, researchers have found many amazing multi-functional properties based on MFIRMT. − It has been reported in 2013 that the refrigerating effect could be enhanced by combining the elastocaloric effect and magnetocaloric effect in Ni 43 Mn 40 Sn 10 Cu 7 FSMAs . Compared to the current mainstream materials La–Fe–Si, Gd–Si–Ge, and so on, Ni–Mn–Sn magnetic alloys are nontoxic, green, and less expensive.…”

Martensitic Transformation, Thermal Analysis and Magnetocaloric Properties of Ni-Mn-Sn-Pd Alloys

“…Once a magnetic field is applied, the change in magnetic entropy (∆S M ) causes the magnetocaloric effect (defined as direct MCE when the total entropy change is negative and inverse MCE when total entropy change is positive) [7]. Among several alloys showing first-order magneto-structural transformation (FOMT), giant MCE has been reported in different Ni-Mn-(Sn,In) alloys [8]. It was also well-identified that in metamagnetic systems, the inverse magnetocaloric occurring on applying isothermal magnetization and adiabatic magnetization relies on field-induced reverse martensitic transformation and the cooling stems from the latent heat of the structural transformation.…”