Rapid formation of the magnetocaloric phase in La-Fe-Co-Si magnetocaloric alloys for near room temperature applications

The effect of La content on the phase formation, microstructural evolution and magnetocaloric properties of off-stoichiometric La _xFe ₁₁Co _0.8Si _1.2 ( x = 1.0, 1.2, 1.4, 1.6) alloys has been investigated. The time for forming a high content of the desired 1:13 phase decreased with an increase in La content, due to the presence of the 5:3 phase and fine α-Fe dendrites. However, excessive La content results in an undesirable La-rich phase. After annealing at 1323 K for 7 days, a high content of the 1:13 phase (>90 wt%), and large maximum magnetic entropy change (‒Δ S _M) ^max of 6.81–7.59 J/kg·K (Δ H = 2 T) in the temperature range 270–278 K was obtained in all samples. Large values of (‒Δ S _M) ^max and tunable Curie temperature ( T _C) along with short annealing time make these alloys promising magnetic refrigeration materials for near room temperature applications.