Studying of doping boron and carbon in LaFe11.6Si1.4 magnetocaloric alloy by experimental and density-functional methods

Both magnetic transition and magnetocaloric properties of LaFe11.6Si1.4 doped with boron (B) and carbon (C) were investigated. Experimental data showed that nearly pure τ1 phase was obtained in LaFe11.6Si1.4, LaFe11.6Si1.4B0.06 and LaFe11.6Si1.4C0.06 alloys after annealing at 1373 K for 100 h. All annealed samples underwent a first-order magnetic transition. B doping decreased the magnetic transition temperature from 192 K to 188 K, whereas C doping increased to 206 K. In combination with X-ray diffraction results, the density-functional theory was used to reconstruct the unit-cell in order to understand the magnetic transition behavior. The results suggested that almost all B atoms occupy 96i FeII/Si substitutional site, and all C atoms prefer 24d interstitial site in the present given conditions. The annealed samples possessed the maximum magnetic entropy changes higher than 20 J/(kg⋅K) under a magnetic field change of 3 T, and their effective refrigeration capacities reached 200 J/kg.