Fast synthesis and magnetocaloric properties of La(Fe, Co, Si)13 compounds and their hydrides

LaFe11.5-xCoxSi1.5 alloys (0 <= x <= 2.2) have been synthetized using high energy ball milling and one of either short annealing treatment or reactive Spark Plasma Sintering. Corresponding hydrides were prepared using a Sievert method. The alloys were characterized by XRD and EPMA and the hydrides by XRD. The physical properties of all compounds were determined using magnetic measurements, DSC and Mossbauer spectroscopy. A significant increase of their cell volume is observed between paramagnetic towards ferromagnetic state. By increasing the Co content a continuous increase of the T-C and the mean hyperfine field B-HF has been observed. The study of corresponding hydrides shows that T-C increase is not a pure additional effect but some electronic interactions between Co and H should be taken into account. Their magnetocaloric properties are a combination of both the influence of Co substitution and hydrogen insertion.