Deconvolution of overlapping first and second order phase transitions in a NiMnIn Heusler alloy using the scaling laws of the magnetocaloric effect

• Published in: Journal of alloys and compounds 2021-08, Vol.871, p.159621, Article 159621
• Main Authors: Díaz-García, Álvaro, Law, Jia Yan, Moreno-Ramírez, Luis M., Giri, Anit K., Franco, Victorino
• Format: Article
• Language: English
• Subjects: Alloys; Deconvolution; Heusler alloys; Magnetic materials; Magnetocaloric effect; Overlapping phase transitions; Phase transitions; Scaling laws; Temperature dependence
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.159621

•MCE materials with FOPT usually show an additional SOPT.•Deconvolution of both contributions is possible using scaling laws.•In NiMnIn Heusler, the contributions have different sign.•The anomalous decrease of ΔSiso with field for large fields is explained. Magnetocaloric materials with a first order phase transition may exhibit additional thermomagnetic phase transitions in the temperature range of interest due to the second-order magnetic phase transitions of the phases. In the case of Heusler alloys exhibiting magneto-structural transformation (martensitic type), this first-order phase transition is usually accompanied by a temperature dependence of magnetization of the different magnetic structures. The temperature of the martensitic transition in this type of materials can be tuned by altering the composition, making possible a close proximity between this transition and the Curie transitions (second-order type) of the structures. This can result in a tight overlap between the two types of magnetocaloric effects, usually of different signs. In this work, the magnetocaloric response of overlapping first and second-order phase transitions of a Ni48.1Mn36.5In15.4 Heusler alloy has been deconvoluted by applying the scaling laws of the magnetocaloric effect. This deconvolution allows the prediction of the magnetocaloric response of the pure first-order phase transition, helping to gauge if it is worth synthesizing other alloys of the same family for which the Curie transition would be much more distant. The deconvoluted signal confirms that the anomalous experimental decrease of ΔSiso with increasing the field above ~ 3 T is due to the competing contribution of the overlapping second-order phase transition.