Virgin effect in spheres of LaFeSi-based alloys

A virgin phase transition is observed in spherical particles of the industrially relevant magnetocaloric material La(Fe,Mn,Si)13Hy. Upon initial cooling, the phase transition is observed 2–3 K below the heating transition on all subsequent cooling and heating transitions. This virgin transition has been studied using differential scanning calorimetry and vibrating sample magnetometry. Incremental measurements show not only how the phase transition can be carefully approached but also that the initial full transformation requires cooling of about 6 K below the observed phase transformation. No signs of structural damage due to the thermal cycling were observed, neither macroscopically or by scanning electron microscopy.