Broadening of temperature working range in magnetocaloric La(Fe,Co,Si)13- based multicomposite

The La(Fe,Co,Si)13- based composite sample was obtained by high energy ball milling of LaFe11.8-xCoxSi1.2 alloys (where x = 0.52, 0.66, 0.8, 0.94, 1.08) and subsequent compaction into a form of the single pellet. A motivation for the processing of such composite specimen was the wish to improve the operating temperature range of the magnetocaloric materials at around the room temperature. In order to achieve this task the influence of Co content on the phase constitution and magnetic properties of the LaFe11.8-xCoxSi1.2 alloys (where x = 0.52, 0.66, 0.8, 0.94, 1.08) was studied. The coexistence of two crystalline phases (the dominant La(Fe,Si)13- type and minor α-Fe(Co) in each sample was detected by XRD studies. These observations were confirmed by the Mössbauer spectroscopy. Furthermore, the Mössbauer spectra analysis revealed the evolution of magnetic ordering in the La(Fe,Si)13- type phase for samples of various Co content. These changes of magnetic ordering were related to the increase of the Curie point with the increase of Co content. The highest value of the magnetic entropy change of ∼16.25 J (kg K)−1 was measured for the x = 0.66 sample, though a significant decrease of the magnetic entropy change down to 3.77 J (kg K)−1 was detected for the composite sample. However, a significant broadening of the −ΔSM peak, reaching ∼100 K in comparison to predicted 85 K was observed.