GREAT MAGNETIC ENTROPY CHANGE IN La(Fe, M)₁₃ (M=Si, Al) WITH Co DOPING

Very large magnetic entropy change \DeltaS_M, which originates from a fully reversible second-order transition at Curie temperature T_C, has been discovered in compounds La(Fe, Si)₁₃, La(Fe, Al)₁₃ and those with Co doping. The maximum change \DeltaS_M \approx 19 J·kg^-1·K^-1, achieved in LaFe_11.4Si_1.6 at 209K upon a 5T magnetic field change, exceedsthat of Gd by more than a factor of 2. The T_C of the Co-doped compounds shifts to higher temperatures. \DeltaS_M still has a considerable large magnitude near room temperature. The phenomena of very large \DeltaS_M, convenience of adjustment of T_C, and also thesuperiority of low cost, strongly suggest that the compounds La(Fe,M)₁₃(M=Si, Al) with Co doping are suitable candidates for magnetic refrigerants at high temperatures.