Enhanced room-temperature magnetocaloric effect and tunable magnetic response in Ga-and Ge-substituted AlFe2B2

Abstract It is demonstrated that alloying additions of Ga and Ge enable tuning of the magnetocaloric response of the intermetallic boride AlFe 2 B 2 . Samples of nominal chemical composition Al 1.2-x M x Fe 2 B 2 (M = Ga, Ge; x  ≤ 0.30) were synthesized via suction casting (arc-melting and vacuum drawing into cylindrical copper molds) and subsequent heat treatment (annealed to 1373 K for 72 h). The saturation magnetization ( M s ), Curie temperature ( T c ) and specific heat capacity ( C p ) of the samples all increase with increased Ga and/or Ge additions. Relative to the unmodified parent AlFe 2 B 2 compound, a larger than two-fold improvement in the magnetic entropy change ( Δ S ( μ 0 H app  = 2 T) = 6.5 J kg −1 K −1 ) and adiabatic temperature change ( ΔT ad ( μ 0 H app  = 2 T) = 2.2 K) was observed at 305 K in a sample of composition Al 1.1 Ga 0.05 Ge 0.05 Fe 2 B 2 . The enhanced magnetocaloric response of the Al 1.2-x (Ga,Ge) x Fe 2 B 2 system is ascribed to a complex amalgamation of chemical bonding and electronic effects that arise due to Fe and Al antisite defects within the AlFe 2 B 2 lattice. Overall, these results provide insight of both fundamental and applied relevance concerning pathways for maximizing the magnetocaloric potential of AlFe 2 B 2 for potential energy-related applications near room temperature.