Structural and magnetic properties of magnetocaloric LaFe 13– xSi x compounds synthesized by high energy ball-milling

Abstract

The structural and magnetic properties of the LaFe 11.3Si 1.7 alloy synthesized by arc-melting and the LaFe 13– x Si x ( x = 1.4, 1.6, 1.8, 2.0) series synthesized by high energy ball-milling (BM) have been investigated. The X-ray diffraction (XRD) results show that an almost single 1:13 phase is obtained by BM. No secondary LaFeSi phase was observed for ball-milled samples, which is not the case for the arc-melting synthesis. Moreover, only 30 min of heat treatment are needed for ball-milled LaFe 13– x Si x alloys in order to obtain single phase compounds (30 days in the case of arc-melted compounds). The study of the magnetic properties revealed that the Curie temperature increases with the Si content whereas the magnetic entropy variation decreases. The latter are respectively associated with a change of the Fe–Fe exchange energy and a magnetic dilution caused by the substitution of a ferromagnetic element by a diamagnetic one. It is shown in this paper that BM compounds display similar magnetic behavior as the corresponding bulk alloys. This means that this way to prepare LaFe 13– x Si x compounds with giant magnetocaloric effect is cost-effective.