Hysteresis, latent heat and cycling effects on the magnetocaloric response of (NiMnSi)0.66(Fe2Ge)0.34 alloy

• Published in: Intermetallics 2021-04, Vol.131, p.107083, Article 107083
• Main Authors: Moreno-Ramírez, L.M., Díaz-García, Á., Law, J.Y., Giri, A.K., Franco, V.
• Format: Article
• Language: English
• Subjects: Demagnetization; Hysteresis; Latent heat; Magnetocaloric effect; Magnetostructural transformations; Measurement methods; MnNiSi-Based alloys; Phase diagrams; Phase transitions; Room temperature
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2020.107083

In this work, we further analyze the promising magnetocaloric (NiMnSi)0.66(Fe2Ge)0.34 alloy, which presents isothermal entropy change values as large as 29 J kg−1 K−1 for 2 T at room temperature. It undergoes a magnetostructural transition accompanied by large thermal/magnetic hysteresis, which remains up to high magnetic fields (corroborated by the elaboration of an experimental magnetic phase diagram). We illustrate that this huge hysteretic behavior (i.e. different responses when magnetizing or demagnetizing) can lead to erroneous interpretation of the order of the phase transition by applying the conventional Banerjee's criterion or the recently developed field dependence analysis of the magnetocaloric effect. Additionally, the cyclability of the response is characterized, showing that after several measurements the magnetocaloric response is significantly reduced (by ≈ 40%) due to sample breaking. These dependences together with the large latent heat of the transition (15.0 kJ kg−1) lead to relatively small values of the adiabatic temperature change for powdered samples at moderate field changes, reaching around 0.6 K for 1.75 T by direct measurement methods. •(NiMnSi)0.66(Fe2Ge)0.34 shows large ΔsT values at room temperature.•This is accompanied by low reversibility/large hysteresis.•Hysteresis can lead to erroneous interpretation of the order of the transition.•Cycling effect reduces the magnetocaloric response around 40%.•ΔTS is shown to be limited (around 0.6 K at 1.76 T) due to the high latent heat.