Structure, magnetic and magnetocaloric properties of Ni2MnGa Heusler alloy nanowires

Abstract

Heusler alloys are favorable candidates for fabricating functional devices and sensors due to their characteristic structural and magnetic properties, which vary at different length scales. In this paper, for the sake of expanding the fields of application and systematically studying the mechanisms at the nanoscale, Ni2MnGa Heusler alloy nanowires were fabricated via the electrospinning method followed by optimized heat treatments. While the nanowires exhibited ferromagnetic-paramagnetic transition near room temperature, anomalies in magnetic behaviors were observed by power fitting of χ−1-T curves disobeying Curie-Weiss law. The Ni2MnGa nanowires exhibited maximum isothermal entropy change of 0.35 J/kgK accompanied by extremely wide working temperature region (150 K), with a peak temperature (305 K) suitable for room temperature applications. Arrott plots and quantitative analysis of field/temperature dependence of magnetic entropy change determined second order magnetic phase transition in the nanowires. Construction of phenomenological universal curves addressed demagnetizing effect on magnetocaloric response, which was compared to the multiphase composition obtained by structural analysis. These novel findings in Ni-Mn-Ga nanowires enrich our knowledge of structure and magnetism of Heusler alloys at the nanoscale and could be taken as reference facilitating future relevant research.