Structural and magnetic properties of magnetocaloric LaFe_(13-x)Si_x compounds synthesized by high energy ball-milling

摘要

The structural and magnetic properties of the LaFe_(11.3)Si_(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 30min 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 FeeFe 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 BMcompounds display similarmagnetic 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.