Rapidly solidified La(Fe0.88Si0.12)13 alloys and their magnetocaloric properties

La(Fe_0.88Si_0.12)₁₃ and their hydrides show a large magnetocaloric effects which make them the primary candidate for the working materials for a near room temperature magnetic refrigeration.In this paper, structure and magnetocaloric effects of rapidly solidified La(Fe_0.88Si_0.12)₁₃ alloys after short heat treatments are Rapidly solidified La(Fe_0.88Si_0.12)₁₃ alloys were prepared using both a melt spinning method and a strip casting method. A small amount, approximately about 1 g in weight, of the ribbons of the rapidly solidified alloys were wrapped in a thin Nb foil and subjected to annealing at temperatures from 1250 K to 1373 K for various period ranging from 1 minute to 24 hours under an Ar gas flow using an infrared heating furnace. The rapidly solidified alloys contained a significant amount of the La(Fe-Si)13 phase, bcc Fe-Si, and a small amount of other phases such as LaFeSi as revealed by powder X-ray diffraction analysis. Scanning electron microscopy of fractured cross section of the as-spun flake obtained with the surface velocity of 20 m/s has revealed that the mean crystal grain size was about 100 nm. The magnetic part of the enthalpy change, DeltaS_mag near the Curie temperature of the strip-cast alloy after a heat treatment at 1250 K for one hour is given. The La(Fe-Si)₁₃ alloys with sufficiently high homogeneity and a large magnetocaloric effect associated with a sharp magnetic phase transition can be achieved by means of a very short period of annealing of rapidly solidified La(Fe-Si)₁₃ alloys.